Journal
Lion's mane: contraindications and side effects reported in research
Soplówka jeżowata przeciwwskazania: what research reports about lion's mane side effects, who should be cautious, and when to check with a doctor first.
TCM therapist · Doctor of Acupuncture (WFAS) · author of a book on functional mushrooms
4 min read
Contents
Soplówka jeżowata przeciwwskazania: known in English as lion's mane, it is studied mainly for mild stomach discomfort, occasional headaches and rare allergic reactions, though a 2025 systematic review notes that adverse events are typically underreported in the literature. Be cautious with a mushroom allergy, pregnancy, breastfeeding, and prescription medication, and check with a doctor first.
What do studies actually report about side effects?
The 2025 systematic review by Menon et al. gathered 26 papers on lion's mane as a supplement, including 5 randomized human trials (PMID: 40959699). The authors describe reported mild stomach discomfort and headaches as the most common findings.
They state plainly, though, that safety documentation in the literature is incomplete, adverse events are sometimes simply not reported in publications. That's a data gap, not proof of complete safety.
Who should be especially cautious with lion's mane?
The studies in our review contain no data on children or on people with thyroid conditions, including Hashimoto's; no data does not mean safety, so in these groups the decision to supplement is best discussed with a doctor, especially since reactions can differ between individuals.
Three groups should talk to a doctor before starting: people with a mushroom allergy (lion's mane is a mushroom, so cross-reactivity is possible), pregnant and breastfeeding women (no safety studies for this group appear in our literature review), and people on anticoagulants or diabetes medication, due to theoretical interactions described in lab and animal studies. More detail on specific medications is in our separate post on lion's mane interactions.
What the studies checked
The table below lines up the three studies cited in this post: type, sample size, exactly what was checked for safety, and the PMID to verify the source. The Menon et al. row is a systematic review covering the other two clinical trials, so read it alongside the paragraphs above.
| study (author, year) | type | in whom | what it checked | PMID |
|---|---|---|---|---|
| Menon et al., 2025 | systematic review | 26 papers, 5 RCTs | benefits, side effects and uses of lion's mane as a supplement | 40959699 |
| Mori et al., 2009 | placebo-controlled RCT | 30 people, aged 50-80 | cognitive-scale score after 16 weeks of 3 g/day, no serious events reported | 18844328 |
| Li et al., 2020 | pilot RCT | 49 randomized, 41 completed | safety parameters over 49 weeks of erinacine-A-enriched mycelium | 32581767 |
What these studies don't tell you
None of the studies cited was designed purely to assess safety in a large sample or over many years, so rare adverse events may simply not have been captured. The results come from specific populations (Japan, older adults or healthy adults), not everyone who might take the supplement.
FAQ: frequently asked questions
Does lion's mane have serious side effects? No serious adverse events were reported in the studies cited, but the 2025 systematic review notes that safety reporting in the literature is incomplete. Talk to a doctor if you notice concerning symptoms.
Can someone with a mushroom allergy take lion's mane? Not without checking with a doctor or allergist first. Lion's mane is a mushroom, so cross-reactivity with another known mushroom allergy is possible.
Is lion's mane safe during pregnancy? Our literature review found no safety studies covering pregnancy or breastfeeding. That absence of data is a reason for caution and a conversation with your doctor, not a reason to decide alone.
More on the species is on the lion's mane page, and product details are on the lion's mane product card. What the research actually looked at is covered in the post on lion's mane study areas, and study doses are listed in the post on lion's mane dosage.
This content is for educational purposes only and does not constitute medical advice. A food supplement does not replace a varied diet or a healthy lifestyle. If in doubt, consult your doctor or pharmacist.