Cold Brew and Iced Herbal Tea: Food-Safety Questions
What food-safety agencies say about bacteria and warm, standing drinks, what we could not find about sun tea and cold-brewed herbal tea, and who needs extra care.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
People often ask whether iced herbal tea, tea left in the sun, or tea steeped in cold water is safe. The short, honest answer is that we did not find a food-safety agency page or study we could read that tests sun tea or cold-brewed herbal tea directly. What we could read is general guidance about how bacteria grow in food left at room temperature, plus studies of the dry tea itself. This page describes those sources. It is not a recipe or an instruction, and it is not medical advice.
What we looked for, and what we found
We searched for food-safety guidance and published studies on sun tea, iced tea and cold-brewed tea, and for herbal tea in particular. Proper evidence not found for these questions in the sources we could read: how fast bacteria grow in sun tea, whether cold steeping carries a different risk from hot steeping, and how long iced herbal tea stays safe. A few agency pages, including USDA food-safety pages, could not be opened by our tools, so absence from this page is not proof that other guidance does not exist.
| Question | What the sources we read say | Strength of evidence |
|---|---|---|
| Does warm, standing liquid allow bacteria to grow? | CDC says bacteria can multiply rapidly if left at room temperature or in the "Danger Zone" between 40°F and 140°F. [1] The page is about food in general and does not mention tea. | General food-safety guidance, not tea-specific |
| How long can perishable food sit out? | CDC says never to leave perishable food out for more than 2 hours, or 1 hour above 90°F. [1] The page lists meat, seafood, dairy, cut fruit, some vegetables and cooked leftovers as examples; tea is not listed. [1] | General guidance; whether it applies to herbal tea is not stated |
| Are there microbes on dry herbal tea before it is brewed? | Studies of tea sold in Italy and Latvia found bacteria, molds and mold toxins in dry tea samples, mostly black, green or mixed tea types. [2] [3] | Observational surveys of dry tea; they did not test iced or cold-brewed drinks |
| Does cold water change this? | Proper evidence not found in the sources we read. | None |
Why the dry tea matters for cold steeping
A cold steep does not use boiling water. In the studies we read, the microbes were counted in the dry tea or its contents, so they tell us the leaves can carry microbes before any water touches them. For example, an Italian study of 32 black and green tea products found microbial loads of 1.0 x 10^2 to 2.8 x 10^5 CFU per gram in over 80% of samples. [2] We did not find a source that follows those microbes into a cold-brewed drink, so we cannot say whether this matters in practice. See storing herbal tea for the dry-tea findings.
Who needs extra care
FDA says the very young, the elderly and people with weakened immune systems are at greatest risk of serious consequences from most foodborne illnesses. [4] Anyone in these groups, or anyone pregnant, can ask a pharmacist or clinician about food-safety questions, including herbal tea. See pregnancy and breastfeeding and children and teens for herb-specific points.
Clean equipment
CDC advises washing utensils, cutting boards and countertops with hot, soapy water after preparing each food item. [1] The page does not mention pitchers or tea containers, so how this applies to a tea jug is not described in the sources we read.
What a reader can do
- Check the label of a ready-made iced herbal tea for storage and "use by" wording, since the sources we read did not cover bottled drinks.
- Read what the plant itself needs: some herbs have their own cautions whatever the temperature, for example licorice in blends.
- Ask a pharmacist or clinician if you take medicines or have a health condition. Herbal tea and extract safety gives the wider picture.
- If you feel ill after a drink, seek medical care. In the US, Poison Help is 1-800-222-1222, and 911 is for emergencies.
Frequently asked questions
Is sun tea safe?
Proper evidence not found. We did not find a food-safety agency page or study we could read that tests sun tea. General guidance says bacteria can multiply rapidly between 40°F and 140°F. [1]
How long can iced herbal tea sit out?
For perishable food, CDC says no more than 2 hours, or 1 hour above 90°F. [1] It does not say whether this applies to tea, and we found no tea-specific time limit.
Does cold brewing make herbal tea safer or riskier?
Proper evidence not found in the sources we read. Studies we found counted microbes in dry tea, not in cold-steeped drinks. [2]
Who should be most careful with homemade iced tea?
FDA names the very young, the elderly and people with weakened immune systems as being at greatest risk of serious consequences from most foodborne illnesses. [4]
Does a cold drink change how a herb affects medicines?
Not described in the sources we read. Medicine interactions depend on the plant; see how interactions work.
References
- Centers for Disease Control and Prevention (CDC). Preventing Food Poisoning. Read 2026-10-23.
- Cariddi LN et al. Comparative assessment of the quality of commercial black and green tea using microbiology analyses. BMC Microbiology, 2018. Read 2026-10-23.
- Reinholds I et al. Determination of Fungi and Multi-Class Mycotoxins in Camelia Sinensis and Herbal Teas and Dietary Exposure Assessment. Toxins, 2020. Read 2026-10-23.
- U.S. Food and Drug Administration. What You Need to Know About Foodborne Illnesses. Read 2026-10-23.