Lion’s Mane Side Effects: 10 Trials, 3 Reported Safety Results
Quick Answer: Lion’s mane (Hericium erinaceus) has a short list of reported side effects, but the list is short partly because few studies looked. Of the 10 human studies we checked, only 3 report any safety result in their abstracts: blood tests showed “no adverse effect” in a 16-week trial, 4 people dropped out of a 49-week trial with abdominal discomfort, nausea and skin rash, and a 10-person pilot called it “safe and well tolerated”. Two published case reports describe a serious lung reaction to a lion’s mane extract and an allergic skin rash in a mushroom farm worker. The NIH’s LiverTox database says it “has not been linked” to liver injury. We found no human study of drug interactions, and it is not a psilocybin mushroom. An advertisement for a lion’s mane product appears near the end of this page.
Most pages about lion’s mane side effects repeat the same three words: stomach upset, itching, allergy. This page goes the other way: it lists what each human study actually reported, and says plainly where a study said nothing. For what lion’s mane may do, see our lion’s mane benefits page; for amounts and the question of how much is too much, see how much lion’s mane per day.
What the 10 human studies reported about side effects
We read the abstract of every human study of lion’s mane we could find in PubMed, plus the full text of one trial that described how it collected side effects. Here is what each one says about safety.
| Study | Who and how long | What it reported on side effects |
|---|---|---|
| Mori 2009 | Adults with mild cognitive impairment, dried fruiting-body tablets, 16 weeks | “Laboratory tests showed no adverse effect” |
| Li 2020 | People with mild Alzheimer’s disease, erinacine A-enriched mycelium, 49 weeks | 4 dropped out “due to abdominal discomfort, nausea, and skin rash”; “no other adverse events were reported” |
| Evans 2026 | 10 healthy adults, 2 g a day, 28 days, no placebo group | Authors conclude it is “safe and well tolerated” in this small pilot |
| Saitsu 2019 | Adults, cognitive function | States oral intake “is safe”; the abstract gives no side-effect data |
| Docherty 2023 | 41 healthy young adults, 1.8 g a day, 28 days | The methods say participants “reported any adverse health outcomes”; we found no side-effect results in the published text |
| Surendran 2025 | 18 adults, single dose | Not mentioned in the abstract |
| La Monica 2023 | Adults, single dose | Not mentioned in the abstract |
| Nagano 2010 | 30 women, cookies, 4 weeks | Not mentioned in the abstract |
| Vigna 2019 | 77 adults with overweight or obesity | Not mentioned in the abstract |
| Xie 2021 | 13 adults, 7 days | Measured serum biochemical markers; no side-effect result stated in the abstract |
So 3 of the 10 report a safety result, and one more asserts safety without data in its abstract. The rest are silent. That silence is the main finding: “no side effects reported” in most of these studies means nobody wrote any down in the abstract, not that people were watched closely and nothing happened.
A 2025 systematic review reached the same place. After reviewing the human studies, Menon and colleagues wrote that “although commonly unreported, potential side effects of HE include stomach discomfort, headache, and allergic reactions.” The phrase that matters is “commonly unreported”.
The one trial that named side effects
Li 2020 is the only trial in our list that names specific side effects, and it ran the longest, at 49 weeks. Four participants left the study with abdominal discomfort, nausea and skin rash. The abstract does not say which group those four were in, so we cannot tell whether they took lion’s mane or placebo. The product was a mycelium extract enriched in erinacine A, made by a company that employs some of the authors, which is a different material from the fruiting-body powders most supplements sell.
Allergic reactions: the two case reports
Searching PubMed for case reports turned up two that involve lion’s mane directly.
- A serious lung reaction (2003). Doctors in Japan described a 63-year-old man admitted for “severe acute respiratory failure with diffuse infiltration in both lungs”. A lymphocyte test “showed a strong reactivity against extract formulation of Hericium erinaceum (Yamabushitake)”, which he had been taking as a diet food. He recovered on steroids and mechanical ventilation. The authors call it “the first report suggesting a causal relationship”.
- A skin allergy at work (1999). Dermatologists in the Netherlands reported occupational allergic contact dermatitis in a person handling the mushroom, sold there as “White Pom Pom”. This was contact with the fresh mushroom at work, not a supplement.
A third report sometimes cited is a 2025 case of liver inflammation in a woman with colorectal cancer who took a capsule containing both lion’s mane and Agaricus blazei. Her doctors concluded the reaction “appeared to be linked to ABM consumption”, meaning the Agaricus, so we do not count it against lion’s mane.
Two case reports across decades of use as a food and supplement is a small number. But anyone with a known mushroom allergy has a clear reason to avoid it, and a new rash, wheezing or breathlessness after starting it is a reason to stop and see a doctor.
Is lion’s mane bad for your liver?
LiverTox, the US National Institutes of Health database on drug-induced liver injury, has a lion’s mane entry. Its summary says lion’s mane “is generally recognized as safe and has not been linked to serum enzyme elevations during therapy nor to episodes of clinically apparent liver injury.”
Animal toxicology points the same way, with the usual caveat that rats are not people. A 13-week rat study of erinacine A-enriched mycelium at up to 2,625 mg per kg of body weight found “neither any mortalities nor noticeable toxicological effects”. Some of its authors work for the company that makes that mycelium. A 2025 study of a commercial lion’s mane powder in rats, run partly by the ingredient’s supplier, also reported no acute or subchronic toxicity.
Lion’s mane drug interactions
We found no human study of lion’s mane interacting with any medicine. Searching PubMed for lion’s mane and drug-metabolising enzymes, blood thinners and blood sugar in people returned nothing relevant. Lists online that warn about blood thinners or diabetes drugs are extrapolating from laboratory or animal work, not from interactions seen in patients.
That is not the same as proof of no interaction. It means the question has not been tested. If you take a blood thinner, diabetes medicine, immunosuppressant or chemotherapy, the sensible step is to tell your doctor or pharmacist before adding any mushroom supplement, as the cancer case above illustrates.
Does lion’s mane make you high? Is it psychedelic?
No. “Magic mushrooms” get their effect from psilocybin, which the US Drug Enforcement Administration describes as coming “from certain types of psilocybe mushrooms”. Lion’s mane is a different fungus, Hericium erinaceus, and the compounds studied in it are hericenones and erinacines, not psilocybin. None of the human studies or the case reports above describe intoxication or hallucinations, and LiverTox describes it as an edible mushroom used as food.
Who should be careful
- People with a mushroom allergy, given the two case reports.
- Anyone on prescription medicines, because interactions have not been studied.
- Pregnant or breastfeeding women: none of the 10 studies enrolled them, so there is no human safety data either way.
- Children: none of the studies enrolled them.
On amounts: the trials gave between about 1 g and 3 g a day, for up to 49 weeks. There is no established maximum, which we cover on the dose page. For differences between powders, capsules and tinctures, see our label comparison.
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Herbal Lab Lion’s Mane Tincture. This is a paid placement, not a recommendation, and it does not change anything above. Herbal Lab’s own Supplement Facts panel lists a 1 mL serving with a “Lion’s Mane Mushroom Botanical Blend” of 1,000 mg, made up of 90 mg of a 10:1 lion’s mane extract described as “equivalent to 900 mg of Lion’s Mane fruit body powder” and 100 mg of lion’s mane powder whose part is not named. None of the studies above tested this product, and side effects have not been studied for tinctures specifically.
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Sponsored link — we may earn a commission at no extra cost to you. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. If you take prescription medicines or have a mushroom allergy, ask your doctor first.
Frequently Asked Questions
What are the side effects of lion’s mane?
The side effects named in human research are abdominal discomfort, nausea and skin rash (four dropouts in one 49-week trial), plus two case reports of allergic reactions: a serious lung reaction to an extract and a contact skin allergy in a mushroom worker. Most trials did not report side effects in their abstracts at all.
Is lion’s mane safe to take every day?
Trials gave it daily for 28 days to 49 weeks without reporting serious problems, and LiverTox says it has not been linked to liver injury. But most trials did not systematically report side effects, so the safety record rests on limited data.
Does lion’s mane interact with medications?
No human interaction study has been published that we could find. Warnings about blood thinners or diabetes drugs are extrapolated from laboratory and animal work. Ask your doctor or pharmacist if you take prescription medicine.
Is lion’s mane bad for your liver?
The NIH LiverTox database says lion’s mane has not been linked to liver enzyme elevations or to clinically apparent liver injury.
Does lion’s mane make you high?
No. It does not contain psilocybin, which comes from Psilocybe mushrooms, and no human study or case report describes intoxication.
Can you be allergic to lion’s mane?
Yes. Published case reports describe an allergic contact dermatitis in a person handling the mushroom and a severe lung reaction linked to a lion’s mane extract. People with mushroom allergies should avoid it.
The Bottom Line
Lion’s mane has few reported side effects, but that is partly because few studies recorded them. Of 10 human studies, 3 report safety results: normal lab tests, four dropouts with stomach upset, nausea and rash, and a small pilot calling it well tolerated. Two case reports show it can cause allergic reactions, including one serious lung reaction. LiverTox finds no link to liver injury, no human study has tested drug interactions, and it is not psychedelic. If you have a mushroom allergy or take prescription medicines, check with a doctor first.
Sources
- Mori K, et al. Improving effects of the mushroom Yamabushitake (Hericium erinaceus) on mild cognitive impairment: a double-blind placebo-controlled clinical trial. Phytother Res, 2009. PMID 18844328. Four 250 mg tablets three times a day for 16 weeks; “Laboratory tests showed no adverse effect of Yamabushitake.” Checked 20 October 2026.
- Li IC, et al. Prevention of Early Alzheimer’s Disease by Erinacine A-Enriched Hericium erinaceus Mycelia Pilot Double-Blind Placebo-Controlled Study. Front Aging Neurosci, 2020. PMID 32581767. Three 350 mg capsules a day (about 1 g) for 49 weeks; “four subjects who dropped out of the study due to abdominal discomfort, nausea, and skin rash”; authors include Grape King Bio staff. Checked 20 October 2026.
- Evans C, et al. A Pilot Proof-of-Concept Study to Evaluate the Physiological and Cognitive Impacts of Hericium erinaceus on Healthy Adults. Nutrients, 2026. PMID 42884628. n = 10, 2 g/day, 28 days; “safe and well tolerated”. Checked 20 October 2026.
- Saitsu Y, et al. Improvement of cognitive functions by oral intake of Hericium erinaceus. Biomed Res, 2019. PMID 31413233. Checked 20 October 2026.
- Docherty S, et al. The Acute and Chronic Effects of Lion’s Mane Mushroom Supplementation on Cognitive Function, Stress and Mood in Young Adults. Nutrients, 2023. PMID 38004235; full text PMC10675414: “Participants reported any adverse health outcomes to assess tolerability and side effects”. 41 adults, 1.8 g/day, 28 days. Checked 20 October 2026.
- Surendran G, et al. Acute effects of a standardised extract of Hericium erinaceus (Lion’s Mane mushroom) on cognition and mood. Front Nutr, 2025. PMID 40276537. 18 adults, single dose. Checked 20 October 2026.
- La Monica MB, et al. Acute Effects of Naturally Occurring Guayusa Tea and Nordic Lion’s Mane Extracts on Cognitive Performance. Nutrients, 2023. PMID 38140277. Checked 20 October 2026.
- Nagano M, et al. Reduction of depression and anxiety by 4 weeks Hericium erinaceus intake. Biomed Res, 2010. PMID 20834180. 30 women, 4 weeks. Checked 20 October 2026.
- Vigna L, et al. Hericium erinaceus Improves Mood and Sleep Disorders in Patients Affected by Overweight or Obesity. Evid Based Complement Alternat Med, 2019. PMID 31118969. 77 adults. Checked 20 October 2026.
- Xie XQ, et al. Influence of Short-Term Consumption of Hericium erinaceus on Serum Biochemical Markers and the Changes of the Gut Microbiota: A Pilot Study. Nutrients, 2021. PMID 33800983. 13 adults, 7 days. Checked 20 October 2026.
- Menon A, et al. Benefits, side effects, and uses of Hericium erinaceus as a supplement: a systematic review. Front Nutr, 2025. PMID 40959699. “Although commonly unreported, potential side effects of HE include stomach discomfort, headache, and allergic reactions.” Checked 20 October 2026.
- Nakatsugawa M, et al. Hericium erinaceum (yamabushitake) extract-induced acute respiratory distress syndrome monitored by serum surfactant proteins. Intern Med, 2003. PMID 14714963. 63-year-old man; “severe acute respiratory failure”; recovered with steroid pulse therapy under mechanical ventilation. Checked 20 October 2026.
- Maes MF, van Baar HM, van Ginkel CJ. Occupational allergic contact dermatitis from the mushroom White Pom Pom (Hericium erinaceum). Contact Dermatitis, 1999. PMID 10344494. Title only; no abstract. Checked 20 October 2026.
- Strobbe G, et al. Grade 3 cytolysis in a patient with metastatic colorectal cancer consuming a mushroom powder-based alternative therapy. J Oncol Pharm Pract, 2025. PMID 39223928. 43-year-old woman; supplement contained Agaricus blazei and Hericium erinaceus; cytolysis “appeared to be linked to ABM consumption”. Checked 20 October 2026.
- LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Lion’s Mane. National Institute of Diabetes and Digestive and Kidney Diseases; updated 5 January 2024. PMID 38289992. “Generally recognized as safe and has not been linked to serum enzyme elevations during therapy nor to episodes of clinically apparent liver injury.” Checked 20 October 2026.
- Lee LY, et al. Thirteen-Week Oral Toxicity Evaluation of Erinacine A-Enriched Lion’s Mane Medicinal Mushroom Mycelia in Sprague-Dawley Rats. Int J Med Mushrooms, 2019. PMID 31002635. Doses 875, 1,750 and 2,625 mg/kg; “neither any mortalities nor noticeable toxicological effects”; authors include Grape King Bio staff. Checked 20 October 2026.
- Mahadevan K, et al. A toxicological assessment of Hericium erinaceus (Lion’s mane) and Trametes versicolor (Turkey tail) mushroom powders. Front Toxicol, 2025. PMID 41230556. Rat study of a commercial powder; authors include M2 Ingredients staff. Checked 20 October 2026.
- Herbal Lab, Lion’s Mane Mushroom Tincture product page and Supplement Facts: 1 mL serving, “Lion’s Mane Mushroom Botanical Blend” 1,000 mg, 90 mg of 10:1 extract “equivalent to 900 mg of Lion’s Mane fruit body powder”, 100 mg lion’s mane powder. hebslab.com. Checked 20 October 2026.
- US Drug Enforcement Administration. Psilocybin drug fact sheet: “Psilocybin comes from certain types of psilocybe mushrooms.” dea.gov. Checked 20 October 2026.
