How Herbal Tea Is Prepared

There is no single method for every herb. The EU's herbal medicines committee (HMPC, part of the European Medicines Agency) says that for herbal teas the way a drink is prepared can matter, because different preparations may have different actions and, in some circumstances, a different safety profile. [1] It also says the strength of a tea varies with how the plant was grown, harvested, dried and stored, as well as with how the tea is made. [1]

This page describes what sources say. It is not a recipe and not advice. For any product, follow its label, and ask a pharmacist if you are unsure. Plants with documented toxicity are not suitable for home tea-making; see comfrey, coltsfoot and pyrrolizidine alkaloids in teas.

The three methods in EU wording

The terms below come from a 2016 HMPC template for patient leaflets of authorized herbal tea products (EMA/HMPC/30603/2012). Times are what the template says "when not otherwise specified". Individual products can differ. For the plain-language meaning of each word, see infusion, decoction and maceration defined.

The template adds that a decoction is generally not applicable to herbs with volatile active constituents, that boiling water matters for lowering the microbial load of the herb, and that gentle warming above room temperature but short of boiling is called "digestion". [1]

Other points from the template

• The template's wording says to keep the preparation covered with a lid while it steeps, stirring at regular intervals. [1]
• Loose herbs are filtered through a tea strainer, and the residue may be pressed; sachets may be gently squeezed. [1]
• A hot infusion is to cool to an appropriate temperature before drinking. [1]
• A tea mixture can need more than one method, for example roots macerated or decocted and mint infused at the end. [1]
• Instant herbal teas, which are only reconstituted with water, are outside the template. [1]

What the cup can contain

Preparation changes what ends up in the drink, but we found little human research on that.

• Lab chemistry: a study of chamomile (Matricaria chamomilla L.) and St. John's wort (Hypericum perforatum) measured plant compounds in infusions and decoctions. Longer extraction time changed the rutin content of St. John's wort and had little effect on antioxidant activity in chamomile. [2] This is a laboratory measurement, not a health outcome.
• Unwanted compounds: a Swiss food-safety authority study of ten naturally contaminated teas and herbal teas found 38 to 100 percent (median 95 percent) of pyrrolizidine alkaloids moved from the herb into the brew when made by the vendor's instructions. [3] The study was about contamination, not a benefit; see the page on pyrrolizidine alkaloids linked above.
• Germs: in Malaysian herbal medicines, boiled decoctions had significantly fewer microbes than non-boiled ones. [4]
• Pesticides and metals: a study of 122 chrysanthemum and Lusterleaf Holly tea samples from China found pesticides in almost all, with about 40 percent of some above EU limits, though its risk assessments were acceptable. [5] A study of herbal teas from Sabac, Serbia found cadmium and lead below detection. [6] These are small local studies and do not describe every product. See heavy metals in herbal tea.

Very hot drinks and tea bags

The International Agency for Research on Cancer (IARC, part of WHO) classified drinking very hot beverages, above 65 degrees C, as probably carcinogenic to humans (Group 2A) for cancer of the esophagus, based on limited evidence, and said it appears to be the temperature rather than the drink. [7] See very hot tea and esophageal cancer risk.

Tea-bag material also matters. A 2026 systematic review of 19 studies found plastic-containing bags released very large numbers of micro- and nanoplastic particles in hot water, and said human health risk assessments are lacking. [8] See loose leaf vs tea bags.