Can a Mushroom Allergy or Intolerance Cause Digestive Issues?

If you experience gastrointestinal symptoms after eating mushrooms, it may be a sign of a mushroom allergy (an immune condition that causes allergic symptoms) or a food intolerance. If mushrooms trigger an allergic reaction, your digestive system can be involved. A food allergy may cause nausea, vomiting, and diarrhea, according to Cleveland Clinic. It can also trigger a more severe reaction called anaphylaxis. Anaphylaxis is considered a life-threatening emergency.

It’s also possible to experience allergic reactions or anaphylaxis with digestive symptoms after eating mushrooms if you have a type of immune system dysfunction called mast cell activation syndrome (MCAS), according to research. In MCAS, you don’t have an allergy to mushrooms specifically, but your immune system can be triggered by harmless substances. While MCAS has been considered a rare disease, the number of people getting diagnosed is increasing, and it has been connected to long COVID.

A food intolerance is also a possibility if you experience gastrointestinal symptoms related to eating mushrooms, per Cleveland Clinic. When your digestive system can’t break down certain foods, you may experience symptoms such as gas, diarrhea, and abdominal pain. Food intolerances can cause painful symptoms, but they’re never life-threatening.

Allergic Reactions

An allergy to mushrooms occurs when the immune system develops an antibody specific to a protein in the food, according to the American Academy of Allergy, Asthma, and Immunology. When the protein is detected, your immune system releases immunoglobulin E (IgE) antibodies. IgE antibodies trigger immune cells to release chemicals that cause an allergic reaction. Symptoms usually start within a few minutes to two hours after you eat the food, per MedlinePlus.

Allergic reactions can progress to anaphylaxis, which is life-threatening. Call 911 if you experience trouble breathing, an extreme drop in blood pressure, or a loss of consciousness. There is no cure for a food allergy; it’s managed through diet by avoiding the consumption of mushrooms.

According to Juniper Allergy in San Antonio, Texas, if you're allergic to mold, you may experience a reaction when eating mushrooms, and vice versa when you’re exposed to mold if you have a mushroom allergy, though not necessarily.

MCAS reactions involve symptoms in two or more organ systems, per Cleveland Clinic. They may be more severe than typical allergic reactions and can occur within minutes or hours, or even be delayed up to 24 to 48 hours after a trigger, per the Accurate Clinic in Kenner, Louisiana. In addition to gastrointestinal symptoms, you may experience skin involvement like flushing or hives, respiratory symptoms like trouble breathing, or cardiovascular symptoms like increased heart rate or a drop in blood pressure. Like IgE antibody-triggered allergies, these reactions may progress to anaphylaxis. If that happens, you'll require emergency medical attention.

Intolerance Symptoms

Food intolerances cause symptoms within a few hours of eating, per Cleveland Clinic. They can be dose dependent, meaning that the amount of food you ingest may dictate how severe the reaction is — you may be able to tolerate a small amount of mushrooms, for instance. In addition to gas, bloating, diarrhea, and abdominal pain, you may experience heartburn or reflux, nausea, and headache or migraine. These symptoms, though they may be painful, are not life-threatening like allergic reactions.

Some people are intolerant to certain carbohydrates found in mushrooms that are poorly absorbed by the gut, called FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols), according to the IBS Clinics in London. FODMAP intolerance can cause digestive symptoms like gas, bloating, and abdominal pain. These intolerances can’t be confirmed via testing.

Allergy Testing

To determine whether you have an allergy to mushrooms, you need to see an allergist and discuss whether testing is appropriate. You may be subjected to skin and blood tests, as well as tests during which you eliminate or eat specific potential allergens, according to MedlinePlus.

During a skin prick test, a small amount of liquid containing the potential allergen’s protein is placed on your skin. Your doctor will prick your skin with a needle, allowing the liquid to get below the skin’s surface. After waiting for 15 to 30 minutes, you’ll check to see if a red, itchy bump has formed, indicating a potential allergy.

Allergy blood tests measure IgE antibodies in your blood. With food allergies, antibody levels specific to that food may be higher than normal, but IgE levels can’t confirm an allergy or its severity. A blood test may be used with other tests to confirm an allergy, however.

Elimination diets have you to remove suspected triggers like mushrooms from your regular diet for a period of time, often two weeks. After the elimination period, you'll slowly reintroduce foods one by one and record how your body responds. Symptoms that occur with reintroduction may indicate an allergy or an intolerance, so this test is often used in conjunction with others.

An oral food challenge test is done under close supervision, and it’s the most accurate food allergy test. It can even be used alone to diagnose IgE-mediated food allergies. During the test, you’ll slowly eat increasing amounts of the suspected allergen. If you don’t react to the food, you don’t have an IgE antibody-mediated allergy. If you do react, you’ll receive immediate treatment, and the allergy is confirmed.

It’s possible to have both IgE-mediated allergies and MCAS, according to research.

To diagnose MCAS, multiple elements are considered. First, you must have a history of recurring episodes of severe reactions that affect two or more organ systems. Your allergist or immunologist will administer urine and blood tests that measure the levels of chemicals released by mast cells or what remains in your system after they’re broken down. Your doctor will also consider your response to medications that block the absorption or prevent the release of mast cell chemicals such as antihistamines, mast cell stabilizers, and certain biologic medications. If these medications prevent or lessen reactions, a diagnosis of MCAS is supported.

Diagnosis and Next Steps

If you test positive for a mushroom allergy, your doctor will recommend that you stop eating all types of mushrooms, as well as mushroom powders, supplements, and broths and seasonings that are mushroom-based, per Juniper Allergy. Mushrooms can be hidden in unexpected foods, such as meat substitutes, so always check labels. You’ll be prescribed an epinephrine auto-injector (EpiPen) or nasal spray (Neffy), as even mild reactions can progress into anaphylaxis, according to the Food Allergy and Anaphylaxis Connection Team.

If you’re diagnosed with MCAS, you’ll also need to avoid triggers, research says. As Mast Cell Action notes, triggers can change over time — what sets off symptoms now may not bother you later. Additionally, MCAS follows a relapsing-remitting pattern, meaning there will be periods of flare-ups and times when you experience few if any symptoms, research says. As with an IgE allergy, you’ll be prescribed epinephrine in case of emergencies. Treatments include antihistamines, mast cell stabilizers like cromolyn sodium (Gastrocrom), omalizumab (Xolair), leukotriene modifiers such as montelukast (Singulair), tyrosine kinase inhibitors such as midostaurin (Rydapt), and corticosteroids.

An MCAS treatment plan often includes multiple medications, as well as an anti-inflammatory diet and foods and supplements that contain quercetin and vitamin C, says Tania Dempsey, MD, an MCAS specialist at the AIM Center for Personalized Medicine in Purchase, New York. Because MCAS can be hard to diagnose and treat, and is often triggered by stress, many people are advised to try lifestyle modifications like stress management, regular exercise, and improved sleep hygiene.

If you have a mushroom intolerance, you’ll need to limit or eliminate them from your diet, per Cleveland Clinic. You may be able to tolerate mushrooms in small amounts, however. When symptoms occur, medications like anti-diarrheals and antacids can help.