Mushroom Coffee Side Effects and Who Should Be Careful
Caffeine effects plus mushroom-specific cautions for mushroom coffee: pregnancy limits from official sources, rash and allergy reports, liver and kidney case reports, and who should ask a clinician first.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
Get help first if this happens
Call 911 for trouble breathing, swelling of the face or throat, or fainting after eating or drinking a mushroom product. Mushroom allergy that causes anaphylaxis (a severe, sudden allergic reaction) is uncommon but has been reported. [1] For severe abdominal pain, or any warning sign of liver or kidney trouble, contact a clinician promptly; the case reports below involved the liver and kidneys, and liver safety lists warning signs. A new rash with whip-like streaks should also be seen by a clinician. [2]Two sources of side effects
Mushroom coffee can cause problems for two different reasons: the caffeine (if the drink contains coffee) and the mushroom. The sources we read do not describe a controlled study of mushroom coffee side effects. Proper evidence not found: a PubMed search of titles and abstracts for "mushroom coffee" returned one dermatology report. What follows is therefore built from caffeine guidance and from reports about the mushrooms themselves, and a result for one mushroom or one form does not carry over to another.Caffeine side effects
The FDA lists these signs of too much caffeine: increased heart rate, palpitations, high blood pressure, sleep disruption, anxiety, jitters, upset stomach, nausea and headache. [3] MedlinePlus adds restlessness, dizziness and dehydration, and says stopping suddenly after regular use can cause headaches, drowsiness, irritability and trouble concentrating. [4] The FDA notes that people differ in sensitivity, and that some conditions and medicines increase it. [3]Who should be careful
| Group | What the sources say | Source |
|---|---|---|
| Pregnancy | NHS: do not have more than 200 mg of caffeine a day; too much has been linked to a higher chance of miscarriage and stillbirth. ACOG (a 2010 opinion): under 200 mg a day does not appear to be a major factor in miscarriage or preterm birth, while the effect of high intake is unsettled. | [5] [6] |
| Breastfeeding | A small amount of caffeine passes to the baby. | [4] |
| Children | Children can be especially sensitive to caffeine. | [4] |
| Anxiety, sleep problems | MedlinePlus advises checking with a clinician about limiting caffeine. | [4] |
| Reflux or ulcers, heart rhythm problems | Same advice. | [4] |
| People on medicines | Stimulants, certain antibiotics, asthma medicines and heart medicines are named for possible interactions with caffeine. | [4] |
Pregnancy and breastfeeding with mushroom coffee: Proper evidence not found for the mushroom part. We did not read a source on mushroom extracts in pregnancy, so absence of data is not a sign of safety. See pregnancy and breastfeeding and mushroom supplements in pregnancy.
Mushroom-specific cautions
- Rash from shiitake. Flagellate dermatitis is thought to be a hypersensitivity reaction to lentinan, a heat-labile polysaccharide in shiitake, and severe reactions after repeated contact have been described. [2] A 2026 report links it to mushroom coffee. [7] We did not read how common this is.
- Allergy. In one case report, a woman had anaphylaxis after a mushroom omelette; skin tests were positive to button mushroom and also to portobello, enoki, oyster and shiitake. [1] See mushroom allergy.
- Liver. A case report describes acute hepatitis after reishi (Ganoderma lingzhi) powder and alcohol; it resolved on follow-up. [8] The authors note that little is known about reishi combined with other substances. [8] See reishi side effects and liver reports.
- Kidney. Case reports describe oxalate kidney injury after chaga (Inonotus obliquus) powder, and the authors call chaga a potential risk factor for chronic kidney disease. [9] Those reports involved powder, not coffee. See mushrooms and the kidneys.
- Immune-active products and autoimmune disease. A scoping review lists reishi among herbal supplements with the strongest evidence of immune-stimulating properties, for clinicians counseling people with autoimmune skin disease. [10] It does not show harm from reishi coffee. People with autoimmune conditions or transplants should ask first; see autoimmune conditions and transplants.
- Surgery. We read no source on mushroom coffee before an operation. Tell the surgical team about every supplement and drink; see surgery and bleeding.
Quality and unknowns
Contamination and mislabeling are possible with any supplement-style product; see quality testing and certifications. If you think a product caused harm, side effects and reporting explains how to report it. Ask a pharmacist or clinician before combining mushroom coffee with medicines, and never change a prescribed medicine on your own.Frequently asked questions
What are the most common side effects of mushroom coffee?
No study we read measured them. If the drink contains coffee, expect the usual caffeine effects, such as jitters, nausea, headache and poor sleep. [3]
Can mushroom coffee upset the stomach?
Caffeine can cause an upset stomach, and MedlinePlus advises people with reflux or ulcers to ask a clinician about it. [3] [4] Proper evidence not found for a mushroom-specific effect.
Is mushroom coffee safe in pregnancy?
The caffeine limit the NHS gives is 200 mg a day, and ACOG found under 200 mg a day does not appear to be a major factor in miscarriage or preterm birth. [5] [6] We found no data on the mushroom extract in pregnancy, so ask an obstetric clinician.
Can mushroom coffee make anxiety worse?
Caffeine can cause anxiety and jitters, and MedlinePlus says people with anxiety should check with a clinician. [3] [4] We found no study on the mushroom part and anxiety.
Can I drink it with my medicines?
Caffeine has documented interaction questions with some medicine groups, such as stimulants, asthma and heart medicines. [4] Ask the prescriber or pharmacist, who can check the full label.
References
- Ali SB, Smith W. Agaricus bisporus mushroom anaphylaxis: a case report and review of the literature. J Allergy Clin Immunol Glob, 2024. Read 2026-10-23.
- Nette D, et al. Flagellate Dermatitis Induced by Shiitake Mushrooms: Clinical Features of a Rare but Characteristic Entity. Diagnostics (Basel), 2026. Read 2026-10-23.
- U.S. Food and Drug Administration. Spilling the Beans: How Much Caffeine Is Too Much? Consumer update, US. Read 2026-10-23.
- MedlinePlus (U.S. National Library of Medicine). Caffeine. Read 2026-10-23.
- NHS (UK). Foods to avoid in pregnancy. Read 2026-10-23.
- American College of Obstetricians and Gynecologists (ACOG). Moderate Caffeine Consumption During Pregnancy. Committee opinion (2010, page notes it may be updated). Read 2026-10-23.
- Mijares J, Ramachandran V. Flagellate Erythema From Mushroom Coffee: A Novel Exposure Route for Shiitake Dermatitis. Int J Dermatol, 2026 (online ahead of print; PubMed lists a title only, no abstract). Read 2026-10-23.
- Guedikian R, et al. Ganoderma lingzhi (Reishi Mushroom)-Induced Acute Liver Injury in the Setting of Alcohol Use: A Case Report and Review of the Literature. Cureus, 2023. Read 2026-10-23.
- Lee S, et al. Development of End Stage Renal Disease after Long-Term Ingestion of Chaga Mushroom: Case Report and Review of Literature. J Korean Med Sci, 2020. Read 2026-10-23.
- Weiner JD, et al. Identifying immunostimulatory herbal supplements that may flare autoimmune skin diseases: a systematic scoping review. Lupus Sci Med, 2025. Read 2026-10-23.