Benefits
Studied in adults with generalized anxiety disorder
In a 2009 randomized, double blind trial of 57 adults diagnosed with generalized anxiety disorder, 8 weeks of chamomile extract lowered Hamilton Anxiety Rating Scale scores more than placebo, but the result was marginal (P = 0.047) in a small group. A later trial took people who had already responded to chamomile and tested whether staying on it prevented relapse over 26 weeks; it did not meet its main goal (hazard ratio 0.52, 95% CI 0.20 to 1.33, P = 0.16). Both trials enrolled people with a diagnosed anxiety disorder, so they do not show what chamomile does for everyday stress in a healthy person.
Traditional use as a bedtime tea
Chamomile tea has a long tradition as an evening drink, and apigenin, one of its flavonoids, binds GABA-A receptors in laboratory work. That is a plausible reason people find it settling, but none of the studies cited on this page measured sleep quality, time to fall asleep, or next day functioning. Treat chamomile as a pleasant part of a wind down routine rather than a tested sleep aid, and do not read the laboratory receptor work as proof it works like or better than a sleep medication.
Traditional use for digestive comfort
Chamomile has been used for centuries to settle the stomach, and laboratory work suggests alpha bisabolol and its flavonoids can calm irritation in gut tissue and relax smooth muscle. None of the studies cited on this page tested digestion in people. Functional dyspepsia, colic, gastritis and irritable bowel syndrome are diagnosed medical conditions, and chamomile is not a treatment for them.
Anti-inflammatory activity in laboratory studies
In laboratory studies, chamomile's chamazulene (formed during steam distillation) and alpha bisabolol act on the COX-2 and 5-LOX pathways involved in inflammation. That is test tube and animal level evidence. No human trial cited on this page measured inflammatory markers, and studies of chamomile applied to the skin say nothing about drinking it or taking it in a capsule.
Blood sugar: studied only in people with type 2 diabetes
One small trial gave chamomile tea, 3 g brewed in 150 mL of water three times a day after meals, to 64 people already being treated for type 2 diabetes for 8 weeks. Compared with a water control it lowered HbA1c (p=0.03), insulin and insulin resistance. Two limitations matter: the comparison drink was plain water and the study was only single blind, so participants could tell what they were drinking, and expectation alone can shift these numbers. Everyone enrolled had a diagnosed disease and was under medical care, so it does not show that chamomile lowers blood sugar in healthy people. Alpha glucosidase inhibition and antioxidant effects on beta cells are proposed laboratory mechanisms, not demonstrated ones. Chamomile is not a treatment for diabetes and must never replace prescribed medication.
Mechanism of action
Apigenin GABA-A receptor partial agonism
Apigenin — chamomile's primary flavonoid — binds the benzodiazepine site on GABA-A receptors as a partial agonist, enhancing inhibitory GABA neurotransmission and producing sedative-anxiolytic effects. This receptor binding has been shown in laboratory studies rather than in people, and how much apigenin from a cup of tea or a capsule actually reaches the brain is not well established. Comparisons with prescription sedatives, including claims about tolerance and dependency, have not been tested in the research cited here.
Alpha-bisabolol anti-inflammatory and GI protective activity
Alpha-bisabolol inhibits NF-κB activation, reduces COX-2 expression, and protects gastric mucosa from irritant-induced damage. This work comes from cell and animal models. It has not been shown to translate into measured effects on inflammation or digestion in the human research cited on this page.
Adenosine receptor modulation for sleep
Apigenin also binds central benzodiazepine receptors and modulates adenosine A1 receptors — contributing to sedative and sleep-promoting effects through both GABAergic and adenosinergic pathways simultaneously. These are proposed mechanisms from laboratory research, and no trial cited here tested whether they change sleep in people.
Clinical trials
Relapse prevention trial. All 179 adults with DSM-IV generalized anxiety disorder first took chamomile extract 1,500 mg/day open label, with no placebo group, for 12 weeks. Only the 93 people who responded were then randomized to continue chamomile (46) or switch to placebo (47) for 26 weeks. Primary outcome: time to relapse. (Mao et al. 2016, Phytomedicine)
179 adults with diagnosed generalized anxiety disorder entered the open-label phase; only the 93 who responded to chamomile went on to the randomized 26 week phase.
The trial missed its primary outcome. Relapse was somewhat less frequent on chamomile than on placebo, but the difference was not statistically significant (hazard ratio 0.52, 95% CI 0.20 to 1.33, P = 0.16). HAM-A scores did fall during the first 12 weeks, but everyone was taking chamomile then and there was no placebo group, so that drop cannot be credited to the herb. Because only prior responders continued into the randomized phase, the results do not describe what chamomile would do for an average person. It was generally well tolerated, with mild digestive symptoms the most common complaint.
Randomized controlled trial of chamomile tea (3 g/100 mL three times daily after meals) vs water in 64 type 2 diabetic patients for 8 weeks. Outcomes: fasting glucose, HbA1c, insulin, HOMA-IR, oxidative stress markers. (Rafraf et al. 2015, J Endocrinol Invest)
64 T2DM patients. 8-week intervention.
Chamomile tea lowered fasting blood glucose, HbA1c, insulin and HOMA-IR compared with water, and raised blood antioxidant markers, which are laboratory readings rather than health outcomes. This is a single small trial in 64 people being treated for a diagnosed disease, the comparison group drank plain water rather than a matched placebo tea, and the HbA1c change was modest. It does not show a blood sugar benefit in healthy people, and chamomile must not replace prescribed diabetes medication.