Evidence explainerLion's mane mushroom
Lion's Mane Side Effects: Stomach Upset, Headache and Allergy
Lion's mane is an edible mushroom, and trials report few problems. A 2025 review lists the side effects that do come up.
Key takeaways
- A 2025 systematic review lists stomach discomfort, headache and allergic reactions as side effects of lion's mane [1].
- In a 16-week trial at 3 g/day, laboratory tests showed no adverse effects [2].
- People with mushroom allergies should be cautious, since allergic reactions are among the reported effects [1].
- Human trials have been small and short, lasting 4 to 16 weeks [2][3].
The evidence, graded
Pulled from our monograph evidence tables. Grades follow our evidence-grading policy.
- Grade DImprovedCognitive function scores in older adultsCognitive scale scores rose significantly more than placebo at weeks 8, 12 and 16, then fell significantly 4 weeks after stopping. Laboratory tests showed no adverse effects.
- Grade DMixedMood, sleep and general complaint scores in womenDepression (CES-D) and complaint scores fell from baseline in the lion's mane group; versus placebo, only two complaint items ('insentive' and palpitations) were significantly lower, and concentration, irritation and anxiety only trended lower.
Reported side effects
A 2025 systematic review of 5 randomized trials, 3 pilot trials and laboratory studies concluded that side effects of lion's mane include stomach discomfort, headache and allergic reactions [1].
In the 16-week trial of 3 g/day in older adults, laboratory tests showed no adverse effects [2].
The limits of the data
The trials that report their size enrolled 30 to 41 people, and none lasted more than 16 weeks [2][4]. One 4-week trial gave lion's mane in cookies to 30 women [3].
Anyone with a mushroom allergy, who is pregnant or who takes prescription medicines should talk to a clinician first [1]. For what the trials found on memory, read does lion's mane work.
Mood and anxiety
Searches often ask whether lion's mane causes anxiety. In the 4-week cookie trial, depression and complaint scores fell from baseline in the lion's mane group, and only two complaint items differed from placebo [3].
Quick answers
Can lion's mane affect the liver?
Our sources do not report liver effects; laboratory tests in the 16-week trial showed no adverse effects [2].
Does lion's mane interact with medications?
Our sources do not report specific drug interactions [1]. Ask a pharmacist before combining it with prescription medicines.
Can lion's mane cause headaches?
Headache is one of the side effects listed in the 2025 review [1].
Keep reading
Full monographs
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References
- [1]Benefits, side effects, and uses of Hericium erinaceus as a supplement: a systematic review. Front Nutr, 2025.
- [2]Improving effects of the mushroom Yamabushitake (Hericium erinaceus) on mild cognitive impairment: a double-blind placebo-controlled clinical trial. Phytother Res, 2009.
- [3]Reduction of depression and anxiety by 4 weeks Hericium erinaceus intake. Biomed Res, 2010.
- [4]The Acute and Chronic Effects of Lion's Mane Mushroom Supplementation on Cognitive Function, Stress and Mood in Young Adults: A Double-Blind, Parallel Groups, Pilot Study. Nutrients, 2023.