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Herbal teas are a traditional and generally safe supplement: they contain various bioactive substances (polyphenols, essential oils, etc.), so some may mildly support sleep/relaxation, digestion or comfort during colds, but they are not a substitute for treatment.
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Evidence in humans is often weak; ritual plays a big role: studies tend to be small and varied, so it’s better to expect a “gentle effect”; at the same time, a warm drink, aroma and regular tea ritual can significantly enhance the effect.
Herbal tea, or a herbal infusion, is a beverage prepared by steeping parts of plants (typically the leaves, flowers, fruits, seeds or roots) in hot water. Unlike “true” tea (from Camellia sinensis), it naturally contains no caffeine, although some herbs may have a mildly stimulating or calming effect.
What active ingredients do herbal teas typically contain?
The composition varies depending on the plant species, part (flower vs. leaf), the quality of the raw material and the method of preparation. You will usually encounter these groups of substances:
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Polyphenols (mainly flavonoids, phenolic acids, tannins). Often described as “plant antioxidants.” Flavonoids are among the main bioactive components of many herbal teas.
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Terpenoids and essential oils (volatile oils). These are aromatic substances responsible for the scent and some effects (e.g., in mint or sage). This includes monoterpenes and sesquiterpenes, which may, for example, have antimicrobial or anti‑inflammatory effects.
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Alkaloids, organic acids and other phytochemicals. Some alkaloids are highly biologically active (and in certain plants may be dangerous at higher doses).
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Polysaccharides (e.g., mucilage), vitamins and minerals. Mucilaginous substances can “soothe” mucous membranes, vitamins/minerals contribute more nutritionally than therapeutically (and their amount in tea is variable and often negligible).
What effects can herbal teas have (in general)?
Herbal tea is not “one drink,” but rather a water extract from plant material—leaves, flowers, fruits, seeds, bark, stems, roots—(fresh or dried), and sometimes blends of several types.
Therefore, the effects of individual teas can differ dramatically.
The most commonly described effects of herbal teas
1) Antioxidant action (protection against “oxidative stress”)
Many herbal teas have shown, in laboratory tests, the ability to “scavenge” free radicals, and in some plants, this effect is explained by the presence of specific polyphenols (e.g., ellagitannins).
However, scientists also point out that some common tests may overestimate antioxidant capacity and, by themselves, do not indicate the real effect in the body.
It is also worth mentioning that oxidative stress is necessary for the body. Only its excess is harmful, i.e., when there is no balance between oxidative and antioxidative factors. High intake of antioxidants is not always automatically desirable.
2) Anti‑inflammatory effects
Some herbal teas are reported to suppress inflammatory signals in cell models. For example, reducing markers such as nitric oxide (NO), TNF-α, and prostaglandin E2 (PGE2) in a model of inflammation induced by lipopolysaccharide.
This is one of the mechanistic reasons why some herbs are traditionally used in conditions where inflammation plays a role.
Again, these are primarily data from preliminary studies (animal studies, models), which do not automatically mean that the effect will also occur in humans.
3) Antimicrobial / antibacterial activity
Herbal teas are often studied for their ability to inhibit the growth of microorganisms. A review of studies reports that in some plants, inhibitory effects against a range of bacteria (including problematic strains such as MRSA) have been observed, but these effects often depend on the type of extract (e.g., alcoholic vs. water).
The authors summarise that current research shows varied antibacterial activities, but a deeper understanding and further research are needed for practical use.
In practice, a substance with antimicrobial activity cannot cure an infection in the body.
4) Effect on blood sugar and metabolism
For some herbal teas, there are animal model data and experiments showing reductions in glycemia and improvements in lipid profiles or insulin sensitivity.
In one study using an animal model of type 2 diabetes, there was also improvement in some markers of organ damage and an effect on gut microbiota.
The review also mentions that longer‑term studies (especially in humans) are needed to properly assess the effects on diabetes compensation.
Other research areas
Research is also focusing on other effects of various herbs, including anti‑obesity, hepatoprotective (liver protection), cardioprotective (heart protection), antidepressant, anxiolytic (anxiety), antimalarial, etc.
For example, antiglycation activity (potentially relevant to “ageing” of proteins and longevity) and, in some extracts, immunological effects in laboratory conditions are also mentioned.
1) Sage tea (Salvia officinalis)
What it is: an infusion from sage leaves.
Potential effects:
- Traditionally used for mild dyspeptic complaints (heartburn, bloating), excessive sweating, irritation in the mouth/throat (often as a gargle) and sometimes for minor skin inflammations.
- Contains essential oils (including thujone), phenolic acids (e.g., rosmarinic) and other polyphenols. Some effects are linked to antimicrobial and anti‑inflammatory properties.
Possible risks / when to be cautious:
- Contraindications: hypersensitivity to sage.
- Pregnancy and breastfeeding: due to a lack of data, regular use is usually not recommended.
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Thujone in high doses can be neurotoxic (theoretically also risk of seizures) → it is not advisable to “overdo it” and drink very strong infusions long‑term.
What studies say:
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Currently, there are not many studies examining sage tea in humans. In vitro studies show anti‑inflammatory potential.
2) Chamomile tea (Matricaria recutita)
What it is: an infusion from chamomile flowers.
Potential effects:
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Traditionally used for mild digestive complaints (bloating, mild cramps), during colds and also locally for minor irritation in the mouth/throat or skin irritation.
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Contains flavonoids (e.g., apigenin) and essential oil components (e.g., bisabolol and others), which are being studied for anti‑inflammatory and relaxing effects.
Possible risks / when to be cautious:
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Allergy: In sensitive individuals (especially to plants from the Asteraceae family), it may trigger an allergic reaction.
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Interactions: caution is rarely mentioned when combined with blood‑thinning medications (with regular consumption and concurrent treatment, it is reasonable to be cautious).
What studies say:
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Sleep and psychological well‑being after childbirth: In a randomised study in postpartum women, drinking chamomile tea (once daily) led to improved sleep quality and reduced feelings of “depression” during the period they drank the tea; however, the effect may not have persisted after discontinuation.
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Type 2 diabetes: In a controlled study in people with type 2 diabetes, drinking chamomile tea (3× daily after meals, 8 weeks) led to improvements in some glycemic indicators (e.g., HbA1c, insulin resistance) and selected antioxidant defence markers also improved.
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In one observational study, more regular consumption of chamomile tea was associated with a lower incidence of certain thyroid diseases; however, such results do not prove causation (lifestyle differences may also play a role).
In general, chamomile is among the most commonly described herbal teas, and its effects are linked to flavonoids and monoterpenes.
3) Nettle tea (Urtica dioica / Urtica urens)
What it is: an infusion from nettle leaves.
Potential effects:
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Traditionally used for mild support of urine production (“flushing” the urinary tract in minor complaints) and sometimes as a supportive agent for mild joint complaints.
Possible risks / when to be cautious:
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Contraindications: hypersensitivity; caution in conditions where fluid intake is restricted (e.g., some severe heart/kidney diseases).
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Pregnancy/breastfeeding: due to a lack of data, long‑term use is usually not recommended.
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Adverse effects: occasionally mild digestive issues or skin reactions.
What studies say:
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Lactation: In a placebo‑controlled study in mothers of premature infants, nettle tea led to increased breast milk production, with no change in prolactin levels observed; no adverse effects were reported in the study, and infant weight gain did not differ between groups.
4) Rosehip tea (Rosa canina)
What it is: an infusion from dried rosehips.
Potential effects:
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Rosehips are rich in vitamin C and various polyphenols/carotenoids; traditionally consumed during colds or “for immunity.”
Possible risks / when to be cautious:
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Usually well tolerated, sometimes mild stomach discomfort may occur.
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With regular medication use, general caution is advised (herbs may have interactions).
What studies say:
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There are no clinical studies examining the effect of rosehip tea in humans. Most often, effects are inferred from individual rosehip components or their extracts.
5) Mint tea (Mentha spicata)
What it is: an infusion from spearmint leaves; typically aromatic due to menthol.
Potential effects:
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Traditionally used for relief from digestive complaints (dyspepsia, flatulence), sometimes for a feeling of “heavy stomach.”
Possible risks / when to be cautious:
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In some people, it may worsen heartburn/reflux.
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Caution is often advised with certain biliary problems and with more pronounced liver issues.
What studies say:
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Mint and chamomile are among the most popular herbal teas; for mint, a relaxing effect on the digestive tract is often mentioned, with some findings well described, especially for mint oil.
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Hirsutism and PCOS. 42 women with hirsutism in PCOS; spearmint vs. placebo. After 30 days, there was a reduction in testosterone and changes in FSH/LH; women reported improvement, but objective hirsutism scores did not change.
6) Linden tea (Tilia spp.)
What it is: an infusion from linden flowers.
Potential effects:
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Traditionally used for relief during colds (sweating, increased body temperature) and sometimes for mild stress.
Possible risks / when to be cautious:
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Contraindications: hypersensitivity.
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Pregnancy/breastfeeding: due to lack of data, regular use is usually not recommended.
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In cases of a cold with pronounced warning signs (shortness of breath, high fever, purulent coughing), it is advisable to consult a doctor.
What studies say:
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There are no clinical data in humans for linden tea, and one must “rely” only on traditional practices.
7) Lady’s mantle tea (Alchemilla vulgaris)
What it is: an infusion from the aerial parts of lady’s mantle.
Potential effects:
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Contains mainly tannins (astringent) and other phenolic substances.
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Traditionally used mainly for nonspecific diarrhoea and digestive complaints; in folk practice, also for menstrual issues.
Possible risks / when to be cautious:
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Higher tannin content may irritate the stomach in sensitive individuals or, conversely, promote constipation; theoretically, it may reduce absorption of some minerals (e.g., iron) when taken together.
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In pregnancy/breastfeeding, caution is usually recommended due to lack of data.
What studies say:
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There are no clinical data in humans for lady’s mantle tea, and one must “rely” only on traditional practices. In vitro and in vivo studies show possible anti‑inflammatory and antimicrobial potential.
8) Lemon balm tea (Melissa officinalis)
What it is: an infusion from lemon balm leaves; gently lemony aroma.
Potential effects:
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Traditionally used for mild symptoms of stress, supporting sleep, and sometimes for mild digestive complaints.
Possible risks / when to be cautious:
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Contraindications: hypersensitivity.
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Pregnancy/breastfeeding: due to lack of data, regular use is usually not recommended.
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Practical caution is sometimes recommended in people with thyroid disease or with long‑term, high intake (especially in concentrated forms).
What studies say:
There are no clinical data in humans for lemon balm tea, and one must “rely” only on traditional practices. In vitro and in vivo studies show possible effects on the relaxation of the digestive tract or anticancer effects. However, these results cannot be applied to humans.
9) Hibiscus tea (Hibiscus sabdariffa)
What it is: infusion from dried hibiscus calyces; usually distinctly tart and “fruity” (often also drunk chilled).
Potential effects:
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Traditionally mentioned for supporting healthy blood pressure, and in some people, it may slightly lower blood pressure (typically systolic, i.e., “upper”).
Possible risks / when to be cautious:
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If you have low blood pressure or take blood pressure medications, it is reasonable to expect that effects may add up (in more sensitive individuals, this may result in greater fatigue and dizziness).
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Caution is also advised in people prone to dizziness and in cases of significant dehydration (e.g., during diarrhoea).
What studies say:
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High blood pressure. In one study (65 adults with prehypertension/mild hypertension), 3 cups of hibiscus tea daily for 6 weeks led to a reduction in systolic blood pressure compared to a placebo drink; average arterial pressure also decreased (for some results, statistical significance was borderline).
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In another double‑blind study (60 people with type 2 diabetes and mild hypertension), 2 cups of hibiscus tea daily for 1 month resulted in a decrease in systolic blood pressure (while in the comparison group with black tea, systolic pressure increased); diastolic pressure did not change significantly.
10) Rooibos (Aspalathus linearis)
What it is: “red tea” from South Africa (not a true tea from Camellia sinensis). There is red (fermented) and green (unfermented) rooibos; green generally has a higher polyphenol content.
Potential effects:
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Traditionally used for supporting digestion, for antioxidant effects, or for better immunity and skin health.
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It is naturally caffeine‑free and has a lower tannin content (so it is milder). It also contains polyphenols typical for rooibos, especially aspalathin and nothofagin.
Possible risks / when to be cautious:
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There have been reports of hepatotoxicity (liver damage), so if you have liver problems, it is advisable to consult a doctor.
What studies say:
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6 weeks, 6× 200 ml/day (fermented rooibos) vs. water in adults at risk of cardiovascular disease: after rooibos, total polyphenols in the blood increased and some markers of oxidative stress/redox balance improved; lipid profile also improved (↓ LDL, ↓ TAG, ↑ HDL).
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Blood pressure. After consuming 400 ml of rooibos, there was a decrease in ACE activity (an enzyme related to blood pressure regulation) at 30 and 60 minutes after consumption; changes in blood pressure/heart rate were not convincing.
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Antioxidant capacity. After consuming 500 ml of tea in one study, there was a slight increase in total plasma antioxidant capacity (TRAP), but without changes in triacylglycerols and cholesterol.
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According to a systematic review, results in humans are mixed, and more research is needed.
Tea blends
Tea blends combine several herbs to complement their effects (e.g., relaxation + digestive relief), improve taste and aroma, and make the effect for regular use “more balanced” than with a single dominant herb. In practice, this often means a milder, better‑tolerated infusion, and a greater chance that you’ll make the ritual a regular habit.
Why blends may be suitable
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Synergy: different components can act on different parts of the “problem” (e.g., stress + muscle tension + digestion).
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Better tolerance: instead of a strong tea from one herb, you use smaller amounts of several plants.
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Taste and compliance: pleasant aroma and taste increase the likelihood that you’ll drink the blend regularly.
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Ritual: for sleep, nervousness, or functional digestive complaints, a “warm fragrant drink” is itself a significant part of the effect and works great as a placebo.
Sleep blends
Why they may work: they target calming the nervous system and establishing an evening routine.
What may have an effect:
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Volatile essential oils (terpenes) from aromatic herbs (aroma + relaxation)
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Flavonoids and phenolic acids
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The ritual of a warm drink (slowing down, better transition to rest mode)
Typical ingredients: lemon balm, chamomile, lavender, acacia, linden, passionflower, valerian
Calming blends (for reducing stress/anxiety)
Why they may work: they combine herbs that may support relaxation and calming of the nervous system, with aromatic components that quickly induce a sense of relief (aroma, warm drink, ritual pause). They often do not act “sedatively” like a drug, but rather help to reduce tension, calm the body, and facilitate a return to a calmer state.
What may have an effect:
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Essential oils / volatile aromatic substances (terpenes) – aroma is a strong signal for the brain; it can quickly support relaxation and “switch” from tension to calm.
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Flavonoids and other polyphenols – in some herbs, these are associated with a mild calming effect (often gentle and individually variable).
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The ritual of a warm drink – warmth + slow sipping + a moment without distractions (phone, work) = natural slowing down, sometimes even calming of breath and muscle tension.
Typical ingredients: lemon balm, chamomile, lavender, linden; sometimes also mint (caution with reflux).
Immunity blends
Why they may work: they often target comfort during colds (fluids, warming, throat) rather than “direct immune boosting.”
What may have an effect:
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Polyphenols (antioxidant and anti‑inflammatory potential)
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Essential oils (feeling of “relief” in the airways, local antimicrobial effect in the throat)
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Organic acids and vitamin C (in rosehips, sea buckthorn, etc., variable depending on raw material and preparation)
Typical ingredients: ginger, mate, rosehip, linden, elderflower, thyme, echinacea
Digestion blends
Why they may work: they combine “carminatives” (against bloating) and herbs with mild spasmolytic effects (against cramps).
What may have an effect:
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Essential oils (relaxation of smooth muscle, less flatulence)
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Bitters (support digestion in a feeling of fullness)
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Tannins (astringent effect that may help with diarrhoea, but worsen constipation)
Typical ingredients: mint, raspberry leaf, fennel, anise, caraway, chamomile, lemon balm, ginger. (With reflux, be cautious with mint; with gallbladder issues, be cautious with some “strong” aromatic blends.)
Focus blends
Why they may work: most often they do not act “stimulantly” like caffeine, but rather improve focus indirectly – by reducing nervousness, improving hydration, and a feeling of freshness.
What may have an effect:
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Aromatic essential oils (feeling of freshness, “clearing the head”)
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Polyphenols (general support for metabolic health; effect on focus is more indirect)
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Taste stimuli and ritual (short break, attention reset)
Typical ingredients: rosemary, mint (freshness), ginkgo biloba, lemon grass, ginger; sometimes also green tea/matcha (but that is a “true tea” with caffeine).
Bottom line
Herbal teas have been used for centuries – partly because they are accessible and pleasant, and partly because, for some people, they truly bring relief from common complaints such as nervousness, poor sleep, or digestive discomfort. Some herbs contain substances (e.g., polyphenols or essential oils) that may have biological effects, but when we look at evidence in humans, we often encounter a problem: studies tend to be small, short, use various doses, and sometimes study extracts rather than regular tea, so conclusions are not entirely valid.
On the other hand, herbal teas, when consumed in moderation, generally have a good safety profile, and their benefits may not rely solely on bioactive components – the placebo effect can also work very strongly in a positive sense. A warm drink, aroma, slowing down, and a regular ritual can calm the nervous system and improve the subjective experience of stress, falling asleep and digestion, which can significantly increase how much tea “helps” you.
Warning: If you take any medications regularly, consult your doctor before drinking regular tea. There may be interactions between herbs and medications, and herbs may affect the function of medications.
