Food Allergy Basics and Emergency Signs

Urgent first: when to call 911

In the US, call 911 for any of these signs after eating, or after any exposure to a food a person is allergic to:

• trouble breathing, very fast breathing, wheezing or noisy breathing
• swelling of the lips, mouth, face, tongue or throat, a tight throat or trouble swallowing
• fainting, or being unable to be woken
• sudden confusion, drowsiness or dizziness
• blue, grey or pale skin, lips or tongue
• a child who is limp, floppy or not responding as usual

These come from the NHS (UK), which lists them as signs of a serious allergic reaction needing immediate hospital treatment [1]. The FDA lists swelling of the throat and vocal cords, difficulty breathing and loss of consciousness among allergic-reaction symptoms [2].

If the person has been prescribed an adrenaline (epinephrine) auto-injector, the NHS says to use it immediately and call emergency services even if the person seems better afterward [1]. It also says not to stand or walk during anaphylaxis, even if feeling better, and that anaphylaxis needs treatment in hospital [3]. How to use a device is shown by the prescriber, pharmacist and manufacturer instructions. For other severe reactions to natural products, see Severe Allergic Reactions to Natural Products.

What a food allergy is

MedlinePlus defines a food allergy as an abnormal immune system reaction to certain foods, usually mild but sometimes serious [4]. A food intolerance is different: it also causes symptoms after eating, but they are typically digestive, such as bloating and gas, and it is not an immune reaction [4]. The NHS says symptoms may come straight after eating or days later, and may affect more than one part of the body at once [1]. MedlinePlus says symptoms usually start within a few minutes to two hours, and may differ from one occasion to the next, sometimes depending on how much was eaten [4].

Common symptoms from MedlinePlus and the FDA include hives, flushed skin or rash, tingling or itching in the mouth, swelling of the face, tongue or lips, vomiting or diarrhea, belly cramps, and coughing or wheezing [4][2].

The major allergens

The FDA says more than 160 foods have been identified as causing food allergy, so a person can be allergic to a food outside this list [2]. The NHS gives examples such as celery, mustard, sesame and lupin flour [1]. People with a food allergy may be allergic to more than one food [4].

Allergy and the functional foods on this site

Foods covered in the library that belong to the major groups include milk-based ferments such as yogurt and kefir, soy foods such as miso, tempeh and tofu, tree nuts such as walnuts and almonds, and fish such as oily fish. Studies showing a health association for a food are not a reason to eat it if you are allergic. The sources we read did not name a safe amount of any allergen for allergic people; the FDA says it has not established a threshold level for any allergen [2].

Who is more likely to have a food allergy

MedlinePlus says children and adults can both have food allergies, some children outgrow them, and adults can develop them. Eczema, asthma, hay fever or a family history make a food allergy more likely [4].

Labels

US law requires the food source of a major allergen to appear on packaged food, either in parentheses in the ingredient list or in a "contains" statement [2]. Statements such as "may contain" are advisory and are not required by law [2]. The FDA says people with food allergies should read labels and avoid the foods they are allergic to [2]. See Reading Food Labels.

Related but different: itchy mouth after raw fruit

The NHS describes oral allergy syndrome (pollen food syndrome) as an itchy mouth and throat after eating raw fruit, vegetables or nuts, which is not usually serious and may be helped by eating well-cooked fruit and vegetables [1]. See a clinician if you are unsure which reaction you have.

Seeing a professional

The NHS says to see a GP if you think you or your child may have a food allergy, and describes tests including skin-prick tests, blood tests and supervised diets that avoid the suspected food, as well as a symptom diary [1]. An allergy specialist gives an allergy action plan [1]. The FDA says some symptoms are not always due to a food allergen, so a health care provider should confirm the cause [2]. Infants and children have specific food-introduction questions; see Foods for Babies and Toddlers. Proper evidence was not found, in the sources we read for this page, for any food or supplement that treats or prevents food allergy in a general reader.

The FDA accepts reports of serious allergic reactions to a food product, with details of the product, symptoms and timing [2]. For safety overviews, see Functional Food Safety.