Cold Brew Herbal Tea: The Safer Way to Make It

"Herbal tea" is not tea in the botanical sense. Hibiscus, peppermint, chamomile and rooibos are dried flowers, leaves and stems from other plants, and the BfR describes herbal and fruit infusions as "tea-like beverages" that should always be prepared with boiling water on hygienic grounds. Its explanation, from its press release Boiling water a must for herbal teas:

• In some cases, germs such as bacteria, yeast or mould may be present in products of plant origin, and in isolated cases they may be pathogenic bacteria like salmonella.
• Only adequate heating can kill germs of this kind with any degree of certainty, so consumers should never prepare herbal tea with warm water.
• Incorrectly prepared, contaminated herbal tea can become a major health risk for small children and sick individuals.
• The advice applies to both loose herbs and tea bags.
• Infused tea should not be allowed to stand for several hours, because spores can survive boiling and germinate in warm liquid.

The BfR even rules out hot-water dispensers for herbal tea: their water is typically only 80–85°C, which it says is not enough to reliably kill any germs present.

A Swiss government laboratory made the cold-brew connection explicit in 2024. The Kantonales Laboratorium Basel-Stadt noted that steeping with hot water brings a reduction in germs, and that this germ-reducing step is missing when tea is steeped cold — so cold-steeped tea carries an increased risk of taking in any harmful germs that may be present.

None of this means ordinary herbal tea is commonly contaminated; the BfR's own wording is "in rare cases." It means the heat step is the safeguard, and a plain cold steep removes it. That is the difference between cold brewing true tea and cold brewing herbs.

This method keeps the BfR's heat step and still ends with a cold, smooth pitcher. It works for any loose herbal blend or herbal tea bag.

1. Measure the herbs for the finished volume. Use the amount the package recommends for the total amount of iced tea you want — but plan to brew it in only about half that volume of water.
2. Bring water to a rolling boil. Not a kettle that switched off a while ago, and not a hot-water dispenser; the BfR says dispenser water at 80–85°C is not hot enough.
3. Pour the boiling water over the herbs in a heatproof jug or pot.
4. Steep for at least five minutes, covered. Five minutes is the BfR's minimum; herbal infusions can go longer for a stronger flavor without the bitterness that tea leaves develop.
5. Strain or remove the bags. You now have a hot concentrate.
6. Chill it fast. Add the other half of the volume as cold water, or pour the concentrate over plenty of ice. This brings the temperature down quickly, so the infusion does not stand warm — the BfR warns that heat-resistant spores can germinate if infused tea stands for hours.
7. Refrigerate promptly. The CDC advises refrigerating perishable food within 2 hours (1 hour above 90°F) and keeping the fridge at 40°F or below.

The result tastes closer to cold brew than to "leftover hot tea," because it spends only minutes hot and the rest of its life cold. If you want a softer, rounder flavor, use fewer herbs rather than a shorter hot steep; the five minutes are the safety part, the quantity is the flavor part.

The same principle is how brands make iced tea from hot water: Lipton's family-size method steeps bags in boiling water, then fills the pitcher with ice or cold water. Our how to make iced tea guide covers the concentrate approach in more detail for black and green tea.

Supermarket shelves now carry herbal and fruit blends labelled for cold infusion, with instructions to steep in cold water. These are a different case from ordinary herbal tea, and there is some useful independent testing of them.

In a campaign from January to April 2024, the Kantonales Laboratorium Basel-Stadt collected 15 different cold-brew teas — 13 in Basel-Stadt and 2 in Aargau — and tested them after preparing each one with cold water exactly as its label instructed. Where the label said how long the prepared drink could be kept, the lab stored it for that period and tested it again. It checked for salmonella, Shiga-toxin-producing E. coli and the hygiene indicator E. coli, and counted the spore-formers Bacillus cereus and Clostridium perfringens.

The results were reassuring for those products:

• No salmonella, Shiga-toxin-producing E. coli, C. perfringens or hygiene-indicator E. coli was found in any of the 15 samples.
• One sample contained a single colony-forming unit of B. cereus per gram of tea, which the lab described as harmless if the tea is drunk promptly, since B. cereus usually causes food poisoning only at counts in the hundreds of thousands per gram.
• The lab concluded that the producers of the products it examined have the microbiological risks of cold-steeped tea well under control.

Two practical takeaways follow. Products sold specifically for cold infusion are a reasonable choice for genuine cold brewing, provided you follow the label exactly, including any "drink within" time. And that finding applies to those products, not to ordinary herbal tea bags or loose herbs, which are made with a boiling-water preparation in mind and carry the BfR's hot-water advice.

These are the four herbal infusions people most often want cold. All four are naturally caffeine-free: USDA FoodData Central lists brewed hibiscus and chamomile at 0 mg caffeine, Harvard's Nutrition Source names chamomile and peppermint among naturally caffeine-free herbal teas, and rooibos contains no caffeine. (Yerba mate and guayusa, by contrast, are herbal-style drinks that do contain caffeine.) The table applies the hot-bloom-then-chill method to each; the hot step is the same for all of them.

Herbal tea	Hot step	Chilling notes
Hibiscus	Boiling water, 5+ minutes	Deep red, tart concentrate; takes ice and dilution well
Peppermint	Boiling water, 5+ minutes	Pour over ice; fresh mint leaves can go in at serving
Rooibos	Boiling water, 5+ minutes	Mild and rounded; a good base for fruit slices
Chamomile	Boiling water, 5+ minutes	Delicate; use a little more than for a hot cup so dilution doesn't wash it out

Hibiscus is the herbal tea most associated with cold brewing, and the one where the hot-then-chill method changes the least about the result: it gives up its color and tartness quickly in boiling water and dilutes into a bright iced drink. Our cold brew hibiscus tea page covers sweetening and blends.

Mint is the easiest to freshen at the end. Brew dried peppermint hot, chill it, then add a few clean fresh leaves to the glass for aroma.

Rooibos keeps its smooth, slightly sweet character well when chilled, and pairs with citrus.

Chamomile is the most delicate of the four; if the iced version tastes faint, increase the amount of flowers rather than cutting the five-minute hot steep.

Whatever the herb, the five minutes in boiling water is the fixed part of the recipe. Everything after that — dilution, sweetener, fruit, fresh herbs — is taste.

Once brewed and chilled, herbal iced tea should be treated like any other perishable drink.

Refrigerate it. The CDC's guidance is to keep the refrigerator at 40°F or below and to refrigerate perishable food within 2 hours, or within 1 hour if it has been somewhere above 90°F, such as a hot car or a picnic. A pitcher of iced hibiscus left on the patio all afternoon falls outside that window.

Don't let it stand warm. The BfR's advice is that infused herbal tea should not be left to stand for several hours, because spores that survive boiling can germinate in warm liquid. That is the reason the method above chills the concentrate immediately instead of letting it cool slowly on the counter.

Follow the label for cold-infusion products. If a blend made for cold water gives a "consume within" time, that is the window its maker designed for; the Basel laboratory tested products over exactly those stated windows.

Keep the equipment clean. Use a pitcher you can wash thoroughly, and add fresh garnishes — mint leaves, citrus slices — at serving time rather than leaving them to soak for days.

Be most careful for the most vulnerable drinkers. The BfR singles out small children and sick individuals as the people for whom a contaminated, incorrectly prepared herbal tea can be a major health risk. For them, stick to the boiling-water method.

How long chilled tea keeps in the fridge is covered in our how long does cold brew tea last guide, and the cold brew tea hub covers cold brewing true tea, where the long cold steep is the standard method.

This page is general food-safety information, not medical advice. If you are preparing drinks for an infant, someone who is pregnant, or someone who is ill or immunocompromised, follow the advice of their doctor.