Immune Wellness
Habits for Immune Health: Sleep, Activity, Nutrition, Smoking and Alcohol
Everyday habits cannot make you immune to infections, but several are linked to how well the body copes with them. This page sorts what is well supported from what is only suggestive across sleep, movement, stress, food, smoking, alcohol and hygiene; supplements, vaccines, frequent illness and recovery each have their own pages.
General information, not medical advice. Last updated October 31, 2026. Written by the AlternativeMed editorial team. Not medically reviewed.
Start here
- Protect your sleep first: aim for the 7 to 9 hours experts recommend for adults, with regular bed and wake times.
- Stay active most days, build up gradually, and rest when you are ill rather than pushing through.
- Wash your hands with soap and water, eat a varied diet with plenty of fruit and vegetables, and keep alcohol low and smoke out of your life.
Be careful with
- No habit, food or product can make you immune. Be wary of anything sold as an "immune booster": the evidence for most of them is weak, and some can interact with medicines.
- If you take medicines that weaken the immune system, or have an autoimmune or immune condition, ask your care team before adding herbs, mushrooms or high-dose supplements.
- Habits do not replace vaccines or medical care. Never stop a prescribed medicine because of something you read online.
Get help when
- Repeated, severe or unusual infections, or infections that keep coming back: see a clinician (the frequent-illness page explains what is worth checking).
- Breathing difficulty, chest pain, a very high temperature, confusion, signs of dehydration, or symptoms that get worse instead of better.
- A cold that has not improved after about 10 days, or any infection symptoms in a baby, an older adult, a pregnant person, or someone with a weakened immune system or a long-term condition.
- Ongoing trouble sleeping, or stress that you cannot manage: these deserve support in their own right.
About Habits for Immune Health: Sleep, Activity, Nutrition, Smoking and Alcohol
What this goal means
This goal is about the daily routines that are linked with how well the body copes with everyday infections such as colds and flu: sleep, physical activity, how you handle stress, how you eat, whether you smoke, how much alcohol you drink, and basic hygiene. The aim is to support normal immune function, not to "boost" it.
The immune system is a network rather than a single dial, which is why "boosting" it is an oversimplification. See How the immune system works for the background, and Support Normal Immune Function for what supports it.
1What people notice
Many people find they catch more colds, or feel worse with them, in periods of poor sleep, heavy stress, little movement or heavy drinking. These are common experiences, and research gives partial support for some of them. A cold usually comes on gradually over 2 to 3 days and improves in about 1 to 2 weeks, so an occasional cold is normal and does not mean your immune system is weak.
2What can make it harder
Shorter sleep, chronic stress, smoking, heavy alcohol use, an inadequate diet and little social contact have all been linked in studies with more infections or worse illness. Age matters too: MedlinePlus notes that the immune system becomes less effective as you get older.
Some conditions and medicines weaken the immune system directly. MedlinePlus gives examples such as corticosteroids, medicines for rheumatoid arthritis, inflammatory bowel disease and certain skin conditions, chemotherapy, HIV/AIDS, removal of the spleen and diabetes.
1,3,4Conditions that can be behind frequent infections
If you are getting repeated or severe infections despite good habits, an underlying cause may be worth looking for. This is a job for a clinician, not for self-diagnosis; the pages below explain what is worth checking.
1Realistic expectations
The honest picture is modest. Studies that exposed volunteers to a cold virus found that shorter sleep, higher stress and fewer social ties went with more colds, but these are associations, not proof that changing them prevents colds. A Cochrane review of exercise trials found no clear drop in how many respiratory infections people had, with low-certainty evidence that symptoms were milder. Good habits are worth keeping for your general health, and they may help at the margins, but they will not stop you catching infections.
3,4,5Who this applies to
Healthy adults who want sensible daily routines. Children, pregnant people, older adults, people with long-term conditions and anyone with a weakened immune system need individual advice, particularly about exercise, supplements and infection risk. If your main question is about vitamins and minerals, vaccines, colds and flu, or recovering from an illness, use the linked goals instead.
2Related conditions and symptoms
Getting sick often → Immunodeficiency and autoimmune conditions → Insomnia → Anxiety disorders →
A manageable starting plan
An educational starting point, not a personal prescription. Adjust it to your own situation and any advice from your clinician.
Your first actions
- Pick a regular wake-up time and aim for 7 to 9 hours of sleep.
- Move on most days: work towards 150 minutes of moderate activity a week at your own pace.
- Wash your hands with soap and water at the key moments: before eating, after the toilet, after coughing or sneezing.
- Build most meals around vegetables, fruit, wholegrain starches and a protein food.
Optional additions
- Choose one stress practice you enjoy, such as a walk or short breathing exercise.
- Schedule time with friends or family each week.
- Plan drink-free days and count your units if you drink alcohol.
- Ask a pharmacist or clinician for stop-smoking support if you smoke.
What to track
- Hours slept and bedtimes for two weeks.
- Weekly activity minutes.
- How often you get colds, how long they last, and how severe they are.
- Any supplements or herbs you take and any new symptoms.
When to reassess
Give new habits a few weeks and judge them by how you feel and function, not by whether you ever catch a cold. If you are getting repeated, severe or unusual infections despite good habits, or infections take unusually long to clear, speak to a clinician.
When to seek professional support
- See a clinician for repeated or severe infections, unexplained weight loss, or symptoms that last or worsen.
- Ask a pharmacist before combining supplements or herbs with medicines.
- Contact NHS 111 or a GP (or your local equivalent) if stress or low mood is affecting daily life.
What helps
Ordered by how well the research supports each step. Evidence strength is shown on every card; precautions sit next to the advice.
Start here
Get enough regular sleep
Moderate certaintyAddresses: Linked with fewer colds after virus exposure
Why it may help: In 164 healthy adults given a cold virus, those who slept under 5 hours or 5 to 6 hours a night (measured by a wrist monitor) were more likely to develop a clinical cold than those sleeping more than 7 hours. An earlier study of 153 adults found those averaging under 7 hours were about three times as likely to catch a cold as those averaging 8 hours or more. A major review describes sleep as affecting immune function, being associated with lower infection risk and possibly improving responses to vaccination. Experts recommend 7 to 9 hours a night for adults.
How to apply it: Keep similar bed and wake times every day, make the last hour before bed calm, and keep the bedroom quiet, dark and cool. For a full set of steps, use the sleep goals.
Who it may suit: Almost all adults.
Precautions: These were studies of association in healthy volunteers, from one research group, and do not prove that sleeping more prevents colds. Ongoing sleep trouble deserves its own care.
6,3,7,8,9Build a Healthy Sleep Schedule → Improve Your Sleep Quality → Insomnia →
Be regularly active at a level that suits you
Mixed findingsAddresses: Good for general health; may make respiratory illness milder
Why it may help: A Cochrane review of 14 trials in 1,377 adults found exercise did not reduce the number of acute respiratory infections, but it reduced symptom severity (moderate-certainty evidence from 2 trials) and the number of symptom days over follow-up (low certainty, 4 trials). The overall certainty was low. The NHS guideline for adults is at least 150 minutes of moderate activity or 75 minutes of vigorous activity a week, plus strengthening on at least 2 days.
How to apply it: Choose activity you enjoy, such as brisk walking, cycling or dancing, spread across most days. Build up gradually.
Who it may suit: Most adults. Speak to your GP first if you have not exercised for some time or have medical conditions or concerns (NHS).
Precautions: A review of the exercise-immunology research reports that heavy exertion has been associated with a temporary dip in immune function and a higher risk of upper respiratory infections. Do not exercise hard when you are ill, and rest when you have a fever.
5,10,11Activity, strength and muscle → Return to Your Routine After Illness →
Wash your hands properly and often
Moderate certaintyAddresses: Helps protect you and others from infections
Why it may help: The NHS says washing your hands is one of the easiest ways to protect yourself and others from illnesses including food poisoning, flu and coronavirus. The best ways to avoid catching a cold, it says, are washing hands with warm water and soap, not sharing towels or household items with someone who has a cold, and not touching your eyes or nose.
How to apply it: Wash with soap and water for about 20 seconds: after using the toilet, before eating or handling food, and after blowing your nose, sneezing or coughing. Use an alcohol-based hand sanitiser if soap and water are not available.
Who it may suit: Everyone.
Precautions: Frequent washing can dry the skin; moisturise afterwards. This page relies on health-agency guidance; the wider infection-prevention evidence is covered on the linked page.
12,2Eat a varied, balanced diet that includes enough protein
High certaintyAddresses: Prevents the shortages that clearly weaken immunity
Why it may help: MedlinePlus lists malnutrition, especially too little protein, as a cause of acquired immunodeficiency. The NHS Eatwell Guide advises at least 5 portions of a variety of fruit and vegetables a day, wholegrain starchy foods, some beans, pulses, fish, eggs or meat, some dairy or alternatives, and unsaturated oils in small amounts, with the balance judged over a day or a week rather than every meal. We did not find solid evidence that any single food "boosts" immunity.
How to apply it: Fill about a third of your plate with fruit and vegetables, include a protein food at most meals, and eat regularly. Fresh, frozen and tinned all count.
Who it may suit: Everyone; especially people who are eating little because of illness, low appetite, dieting or limited access to food.
Precautions: The strongest evidence is for severe shortage, not for fine-tuning a normal diet. If you cannot eat enough, or are losing weight without trying, see a clinician.
1,13,14Eating patterns compared → Meet Your Nutritional Needs for Immune Health →
Stay smoke-free, or take steps to quit
Moderate certaintyAddresses: Avoids a clear risk factor for worse influenza and colds
Why it may help: A meta-analysis of 12 observational studies (18,612 people) found people who had ever been active smokers had higher odds of hospital admission (odds ratio 1.5) and intensive-care admission (2.2) after influenza than never-smokers, with no clear link to deaths. Secondhand smoke was linked to admissions only in children under 15. The NHS says smoking can make cold symptoms worse.
How to apply it: If you smoke, ask a clinician, pharmacist or national quitline about support. Keep homes and cars smoke-free around children.
Who it may suit: Smokers, vapers who also smoke, and households with children.
Precautions: These were observational studies of moderate quality. Quitting is best done with support; do not stop or change any prescribed medicine without advice.
15,2Keep alcohol within low-risk limits
Moderate certaintyAddresses: Avoids the clearest alcohol effects on infection risk
Why it may help: A review says even moderate amounts of alcohol influence immune responses, though the effect is often a subclinical weakening that matters only after a further insult such as an infection. Chronic heavy drinking interferes with both innate and adaptive immunity and raises susceptibility to viral and bacterial infections. We did not find a source that sets a safe amount for immunity specifically. For general health the NHS advises not drinking more than 14 units a week on a regular basis, spread over 3 or more days, with several drink-free days.
How to apply it: Count your units, keep to the low-risk guidance, and plan drink-free days. Limit or skip alcohol while you are fighting an infection.
Who it may suit: Anyone who drinks regularly.
Precautions: If you drink heavily, do not stop suddenly without medical advice, because withdrawal can be dangerous. Talk to a clinician.
16,17Additional options
Use everyday ways of managing stress
Low certaintyAddresses: May reduce the effect of stress on infection risk
Why it may help: In a viral-challenge study of 394 healthy adults, the rates of respiratory infection and clinical colds rose in step with higher psychological stress, and sleep, smoking, alcohol, diet and exercise did not explain the link. A later study of 276 adults found that people with recent long-term, threatening stressful experiences were more likely to develop a cold, with stress linked to a failure to dampen inflammation. The NHS suggests practical steps such as being active, talking to someone, planning ahead, splitting big tasks and breathing exercises.
How to apply it: Pick one or two practices you will actually keep, such as a daily walk, a short breathing exercise, or breaking tasks into chunks. See the stress goals for more.
Who it may suit: Anyone with ongoing pressure from work, money, caring or health.
Precautions: The studies show an association between stress and illness; they did not test whether stress-reduction programmes prevent colds. Persistent stress or low mood needs support from a clinician.
4,18,19Keep up varied social connections
Low certaintyAddresses: Linked with fewer colds in one viral-challenge study
Why it may help: In 276 healthy adults, those with more types of social ties (partner, friends, workmates, groups) were less likely to develop a cold, produced less mucus and shed less virus; the relative risk was 4.2 for people with the fewest versus the most types of ties. In another study of 404 adults, perceived social support, and hugging as a sign of support, were linked to less risk from interpersonal conflict and to milder illness among those infected.
How to apply it: Stay in touch with friends and family, and join a group or activity you enjoy.
Who it may suit: Anyone, especially people who feel isolated.
Precautions: Observational findings from a research group in the same lab; they do not prove that adding friends prevents colds. Isolation is a wellbeing issue in its own right.
20,21Rest and stay home when you are ill
Moderate certaintyAddresses: Supports recovery and protects others
Why it may help: The NHS advises getting plenty of rest and drinking lots of fluid when you have a cold, and staying at home and avoiding contact with others if you have a high temperature or do not feel well enough for normal activities. Colds can spread from a few days before symptoms until they finish.
How to apply it: Rest, drink fluids, and use tissues and handwashing to avoid passing it on. Recovery has its own page.
Who it may suit: Anyone with a cold or flu-like illness.
Precautions: Seek advice if symptoms are severe, get worse, or last more than about 10 days.
2Still being studied
Regular movement and immune ageing
Not enough evidenceAddresses: Researchers are studying how exercise relates to the ageing immune system
Why it may help: A review of exercise immunology describes four research areas, including the clinical benefits of the exercise-immune relationship and the effect of exercise on immunosenescence (the gradual weakening of immunity with age), and notes that newer laboratory methods are being used to understand how exercise changes immune function. It is a developing field rather than a source of firm advice.
How to apply it: Nothing specific to do beyond general activity advice; keep following the activity guideline for your age.
Who it may suit: Older adults and active people curious about the science.
Precautions: Do not treat this as a promise that exercise will prevent infections; the Cochrane review did not find that.
11,5Food & nutrition
A balanced pattern is the evidence-based starting point
The NHS Eatwell Guide shows how much of what we eat overall should come from each food group: fruit and vegetables just over a third, starchy foods (preferably higher-fibre or wholegrain) just over a third, then protein foods, dairy or alternatives, and small amounts of unsaturated oils. You do not need the perfect balance at every meal; aim to get it right across a day or a week.
Almost all fruit and vegetables count towards 5 A Day, and fresh, frozen, tinned, dried and cooked-in-dishes versions all count. 80g is one portion; fruit juice and smoothies count once, limited to a combined 150ml a day.
MedlinePlus lists malnutrition, especially too little protein, as a cause of acquired immunodeficiency, so eating enough matters most. We did not find solid evidence that any single food "boosts" immunity: proper evidence not found in the sources we read.
13,14,1Fish, protein and fluids
The NHS suggests at least 2 portions of fish a week, one of them oily, and some beans, pulses, eggs or meat for protein. When you have a cold it advises drinking lots of fluid, such as water, to avoid dehydration, and eating healthy food; small children often lose their appetite for a few days.
13,2Vitamins and minerals from food
The NHS says most people can get the vitamins and minerals they need from a varied, balanced diet. Vitamin D is the main exception in some places: the NHS advises that everyone consider a daily vitamin D supplement during autumn and winter, mainly for bone and muscle health, and says there is not enough evidence to support taking it solely to prevent or treat COVID-19. Nutrients are covered on their own page.
22,13Remedies & supplements
Traditional use, laboratory findings and human trials are kept apart. "Natural" does not mean safe.
Echinacea
Low certaintyStudied form and route: Supplements or teas from the purple coneflower plant
Intended outcome: Cold prevention or a shorter cold
Human evidence: NCCIH says many studies have been done in people and that taking echinacea may slightly reduce your chances of catching a cold; it is unclear whether it shortens a cold, and more research is needed. The NHS says there is little evidence that supplements such as vitamin C, echinacea or garlic prevent colds or help recovery.
Traditional use: Native Americans used the plant medicinally for respiratory tract infections, tooth pain and snakebite, according to NCCIH.
Limits: Products differ by species, part of the plant and preparation, and results are inconsistent.
Interactions and precautions: Some people have allergic reactions, which can be severe; it is closely related to ragweed, daisies and sunflowers. Possible interactions with some medicines and theoretical interactions with immunosuppressants. Pregnancy and breastfeeding: check with a clinician. Ask before giving to children.
23,2Vitamin C, vitamin D and zinc supplements
Low certaintyStudied form and route: Supplements
Intended outcome: Fewer or shorter colds
Human evidence: The NHS says there is little evidence that supplements such as vitamin C prevent colds or speed recovery, and that not enough evidence supports vitamin D taken solely to prevent or treat COVID-19. The NHS does advise considering a vitamin D supplement in autumn and winter for bone and muscle health. The full evidence for each nutrient is on the nutrition page.
Limits: This page does not weigh the trials for each nutrient.
Interactions and precautions: More is not better; very high amounts can cause harm. Ask a pharmacist or doctor if you take medicines or are pregnant.
2,22Hot lemon and honey drink, rest and fluids
Low certaintyStudied form and route: Home care for a cold
Intended outcome: Comfort while you recover
Human evidence: The NHS lists rest, plenty of fluids, healthy food, salt-water gargling (not for children) and a hot lemon and honey drink as ways to ease cold symptoms at home. These ease symptoms; they do not prevent colds.
Traditional use: A familiar home drink for sore throats.
Limits: Comfort measures only.
Interactions and precautions: Do not give honey to babies under 12 months. Do not give hot drinks to small children.
2Therapies & care
Established professional care here means vaccination, treatment of infections by a clinician when needed, and checks for underlying causes when infections are frequent or severe. A clinician can also help with sleep problems, stress, stopping smoking and cutting down alcohol. This page does not recommend medicines or doses, and you should not stop a prescribed medicine on your own.
Cognitive behavioural therapy for insomnia (CBT-I) and sleep support
High certaintyPsychological and behavioural therapy If sleep trouble has lasted for months, a clinician can offer a structured programme or a check for other causes. Sleep has its own pages.
Who it may suit: Adults with ongoing sleep trouble.
Precautions: Do not self-diagnose sleep apnea; loud snoring or gasping at night needs a check.
9Talking therapies and stress support
Moderate certaintyPsychological support The NHS says if stress is affecting your daily life you can contact NHS 111 or talk to a GP, and that in England you can refer yourself for NHS talking therapies. Self-help CBT techniques are also offered. If you are struggling to cope or keep yourself safe, get urgent support now.
Who it may suit: People whose stress is hard to manage alone.
Precautions: Anxiety, panic and trauma have their own condition pages.
19Stop-smoking support
Moderate certaintyClinical and community support The NHS lists stop-smoking services, advice on e-cigarettes to quit, and medicines to help you quit. Ask a clinician or pharmacist what suits you.
Who it may suit: Smokers who want to quit.
Precautions: Ask before using quit-smoking medicines if you are pregnant or have other conditions.
24Vaccination and a check for frequent infections
High certaintyPreventive and clinical care Vaccines and a medical check for repeated or severe infections are part of professional care and are not replaced by habits. See the linked pages.
Who it may suit: Everyone for vaccination advice; people with repeated or severe infections for a check.
Precautions: Tell your clinician about any medicines or supplements you take.
1,7Reduce Your Risk of Common Infections → Understand Why You Keep Getting Sick →
What to avoid
Habits, products and claims that can get in the way. Never stop a prescribed medicine without talking to the professional who prescribed it.
Risks that apply to most people
Chronic short or broken sleep
Moderate certaintyWhy: Shorter sleep before virus exposure was linked with more clinical colds in two studies, and a review links prolonged sleep deficiency to low-grade inflammation.
Who it applies to: Anyone regularly sleeping under 7 hours, including shift workers and parents of young children.
Try instead: Protect a regular sleep window; see the sleep goals if sleep is hard.
6,3,7Smoking and tobacco smoke
Moderate certaintyWhy: Smokers had higher odds of hospital admission after influenza in a meta-analysis, and the NHS says smoking can make cold symptoms worse.
Who it applies to: Smokers and people living with them, especially children.
Try instead: Ask for quit support; keep smoke away from children.
15,2Heavy or frequent drinking
Moderate certaintyWhy: Chronic heavy drinking interferes with innate and adaptive immunity and raises susceptibility to viral and bacterial infections.
Who it applies to: Anyone who drinks regularly above the low-risk guidance.
Try instead: Keep within the NHS low-risk guidance and plan drink-free days; seek help if cutting down is hard.
16,17Not eating enough, especially too little protein
High certaintyWhy: MedlinePlus lists malnutrition, especially too little protein, as a cause of acquired immunodeficiency.
Who it applies to: People with low appetite, restrictive diets, illness or limited food access; older adults.
Try instead: Eat regularly and include a protein food at most meals; see a clinician about unexplained weight loss.
1,13Personal triggers to check
Long periods of high stress without support
Low certaintyWhy: Higher psychological stress went with more respiratory infections and colds in a dose-response manner in one viral-challenge study; long-term threatening stress was linked to a higher risk of a cold in another.
Who it applies to: People facing ongoing work, money, caring or health pressure.
Try instead: Use practical coping steps and ask for support early.
4,18,19Close contact with people who have a cold or flu, shared towels and cups
Moderate certaintyWhy: Colds spread by droplets from coughs and sneezes, which the NHS says can live on hands and surfaces for 24 hours.
Who it applies to: Households, offices and schools during cold seasons.
Try instead: Wash hands often, avoid sharing towels or household items and avoid touching your eyes or nose.
2,12Pushing through intense exercise when you are unwell or run down
Low certaintyWhy: Reviews of exercise immunology report that heavy exertion has been associated with transient immune dysfunction and a higher risk of upper respiratory infections.
Who it applies to: Athletes and people increasing training quickly.
Try instead: Build up gradually, take rest days, and rest when you have a fever or feel ill.
11Products that need caution
"Immune booster" supplements, powders and shots
Low certaintyWhy: The NHS says there is little evidence that supplements such as vitamin C, echinacea or garlic prevent colds or help you get better more quickly. Products vary in content and quality.
Who it applies to: Anyone tempted by immune-support marketing.
Try instead: Put effort into the basics on this page; see the nutrition page for vitamins and minerals.
2Herbs, mushrooms and echinacea if you take immune-suppressing medicines or have an immune condition
Low certaintyWhy: NCCIH notes theoretical reasons to suspect echinacea might interact with immunosuppressants, conflicting evidence on interactions with some medicines, and that some people have allergic reactions that can be severe. Products meant to stimulate the immune system are a particular concern when the immune system is already overactive, as in autoimmune disease.
Who it applies to: People with autoimmune or immunodeficiency conditions, transplant recipients, people having chemotherapy, and anyone on immunosuppressants.
Try instead: Ask the clinician who manages your condition before starting any herb or supplement; do not stop prescribed medicines.
23Echinacea, elderberry, garlic and mushrooms for immunity → Immune wellness safety → Medicine interactions →
Unsupported claims
"You can boost your immune system"
Evidence againstWhy: The immune system is a network of cells and organs rather than a single dial. We did not find solid evidence in the sources we read that any single food or product boosts immunity; the sources support avoiding things that weaken it and keeping to the basics.
Who it applies to: Product labels, social media and wellness marketing.
Try instead: Think "support normal function" and "reduce what weakens it".
1,2"Antibiotics will help my cold"
High certaintyWhy: The NHS says GPs do not recommend antibiotics for colds because they will not relieve symptoms or speed recovery: antibiotics work only against bacterial infections, and colds are caused by viruses.
Who it applies to: Anyone with a cold or flu-like illness.
Try instead: Rest, fluids and symptom care; ask a pharmacist; see a doctor if symptoms are severe or last long.
2"A healthy lifestyle means I do not need vaccines or medical care"
Evidence againstWhy: Habits are linked with how the body copes with infection; they do not replace vaccination or treatment. Vaccines and medical care are covered on the infection-prevention page.
Who it applies to: Anyone weighing vaccination or care.
Try instead: Use habits alongside vaccination and medical advice, not instead of them.
7Common mistakes
Going back to hard exercise or full activity too soon after an illness
Low certaintyWhy: The NHS advises rest and staying at home while you feel unwell, and reviews note heavy exertion has been associated with more infections.
Who it applies to: Active people and busy workers.
Try instead: Return gradually; see the return-to-routine goal.
2,11Using hand sanitiser as a replacement for washing when hands are visibly dirty
Moderate certaintyWhy: The NHS advice is to wash with soap and water, and to use alcohol-based sanitiser only if soap and water are not available.
Who it applies to: Anyone cooking, eating or caring for others.
Try instead: Use soap and water whenever you can.
12Changing everything at once
Low certaintyWhy: Habit changes are easier to keep when you start small. The NHS advises building activity up gradually.
Who it applies to: Anyone starting a new routine.
Try instead: Start with sleep, then add one other habit at a time.
10,9Evidence & safety
What the research shows
The best-supported steps are the basics: not being malnourished, not smoking, drinking within low-risk limits, and washing hands. Short sleep and high stress went with more colds in virus-challenge studies, but these show association rather than proof. Exercise did not reduce how many respiratory infections people had in a Cochrane review, though symptoms may be milder (low certainty). Supplements marketed as immune boosters have little evidence behind them. We did not find solid evidence that any single food boosts immunity.
Limits of the evidence
- Most sleep, stress and social-tie findings come from viral-challenge studies of healthy adults, several from the same research group, and show association only.
- The Cochrane exercise review rated overall certainty as low because of small studies, bias and inconsistency.
- The smoking review was observational, of moderate quality, and found no clear link to deaths.
- We did not find a source setting a safe alcohol amount for immunity.
- Handwashing and diet statements rely largely on health-agency guidance rather than trials read for this page.
- Results from healthy volunteers may not apply to children, older adults or people with immune conditions.
Precautions and interactions
- Immune "boosters" can interact with medicines or may be unsuitable in autoimmune disease; check with the clinician who manages your condition.
- Heavy exertion has been associated with more upper respiratory infections; build up gradually and rest when ill.
- Do not use alcohol, tobacco or supplements as a way to cope with stress.
- Never stop or change a prescribed medicine because of anything on this page.
Life-stage considerations
- Pregnancy and breastfeeding: ask a clinician before using herbs or supplements, including echinacea; follow vaccination advice from your care team.
- Children: secondhand smoke was linked to flu hospital admissions in children under 15; do not give aspirin to children under 16 for colds, do not give honey to babies under 12 months, and check with a paediatric clinician before giving supplements.
- Older adults: the immune system becomes less effective with age (MedlinePlus); infections can become serious faster, so seek advice promptly.
- People with a weakened immune system or long-term conditions: seek advice sooner when cold symptoms start (NHS).
Warning signs
- Shortness of breath or chest pain (the NHS lists both as reasons to see a GP with cold symptoms).
- A high temperature for more than 3 days, symptoms that get worse, or a cold that is not better after 10 days.
- Cold symptoms with a weakened immune system or a long-term condition such as diabetes, or a heart, lung or kidney condition.
- Other signs of a serious infection, such as confusion, a stiff neck with a rash, dehydration, or any illness in a baby: these need urgent medical care. The sources read for this page did not name an emergency number, so use your local emergency number.
- Repeated or unusual infections despite good habits.
Claim checks
Sleeping less makes you more likely to catch a cold
Moderate certaintyIn two virus-challenge studies, shorter sleep before exposure was linked with more colds. These show association, from one research group, and do not prove that more sleep prevents colds.
6,3Exercise prevents colds
Mixed findingsA Cochrane review found no reduction in the number of respiratory infections; symptoms may be milder (low certainty).
5Stress weakens immunity and gives you colds
Low certaintyHigher stress went with more infections and colds in virus-challenge studies. Whether reducing stress prevents colds was not tested in the studies read.
4,18Smoking harms the immune response to flu
Moderate certaintyEver-smokers had higher odds of hospital and intensive-care admission after influenza in observational studies; no clear link to deaths.
15A drink or two does no harm to immunity
Moderate certaintyEven moderate alcohol influences immune responses, though often in a subclinical way; chronic heavy use raises infection susceptibility. A safe amount for immunity was not found.
16Vitamin C, echinacea or garlic prevent colds
Low certaintyThe NHS says there is little evidence. NCCIH says echinacea may slightly reduce the chance of catching a cold, but more research is needed.
2,23A single superfood boosts your immune system
Not enough evidenceWe did not find solid evidence that any single food boosts immunity.
1,13Questions people ask
Can I boost my immune system with habits?
Habits cannot make you immune to infections. They support normal function and avoid things that weaken it, such as too little sleep, smoking, heavy drinking or not eating enough. We did not find solid evidence that any one food or product boosts immunity.
Does lack of sleep make you more likely to catch a cold?
In a study of 164 healthy adults given a cold virus, sleeping under 6 hours was associated with a higher chance of developing a cold than sleeping more than 7 hours. It shows association, not proof. Experts recommend 7 to 9 hours for adults.
Does exercise prevent colds?
A Cochrane review found no difference in the number of respiratory infections, but exercise may make symptoms milder. Certainty was low. Staying active is still good for your general health.
Is too much exercise bad for immunity?
Reviews report that heavy exertion has been associated with temporary immune changes and a higher risk of upper respiratory infections. Build up gradually and rest when you are ill.
Does stress really make you sick?
In virus-challenge studies, people reporting higher stress were more likely to be infected and to develop colds. That is an association; it is not proof that managing stress prevents colds. Stress is worth managing for your wellbeing anyway.
Does smoking weaken immunity?
Smokers had higher odds of hospital admission after influenza in a meta-analysis, and the NHS says smoking can make cold symptoms worse.
Does alcohol affect the immune system?
Yes: even moderate amounts can influence immune responses, and chronic heavy drinking raises susceptibility to infection. The NHS advises not drinking more than 14 units a week on a regular basis.
Do vitamin C or echinacea prevent colds?
The NHS says there is little evidence that they do. NCCIH says echinacea may slightly reduce your chance of catching a cold, but more research is needed, and it can cause allergic reactions and may interact with some medicines.
Are antibiotics useful for colds?
No. Colds are caused by viruses and antibiotics only work against bacterial infections, so GPs do not recommend them for colds.
I take medicine that weakens my immune system. Can I try immune supplements?
Ask the clinician who manages your condition first. Some herbal products may interact with immunosuppressants or may not suit autoimmune conditions. Do not stop your medicines.
When should I see a doctor about getting sick?
See a clinician if infections are repeated, severe or unusual, if a cold lasts more than about 10 days, or if you have shortness of breath, chest pain or a high temperature for more than 3 days. Seek help sooner if you are older, pregnant, have a long-term condition or a weakened immune system.
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Related goals
Support Normal Immune Function → Meet Your Nutritional Needs for Immune Health → Prepare for Cold & Flu Season → Reduce Your Risk of Common Infections → Understand Why You Keep Getting Sick → Support Recovery From Common Illness → Return to Your Routine After Illness → Build a Healthy Sleep Schedule → Manage Everyday Stress →
Ingredients, foods and supplements
Echinacea, elderberry, garlic and mushrooms for immunity → Vitamin C, vitamin D and zinc → Functional foods by wellness goal →
Research, safety and claim-check resources
Immune wellness safety → Immune wellness research and evidence → How the immune system works → Stress → Better sleep → Eating patterns compared → Activity, strength and muscle → Social connection and loneliness → Medicine interactions → Breathwork →