Milk thistle is an herb commonly used to treat fatty liver disease, hepatitis, cirrhosis, gallbladder problems, diabetes, and issues with the spleen. One of the active ingredients in this plant, silymarin, is believed to have antioxidant benefits. This dietary supplement can be consumed as a capsule, tablet, or liquid extract. Clinical trials and individual reports show it is generally useful and not harmful at the recommended dose. However, some people might experience side effects from taking milk thistle.


For most users, gastrointestinal problems are the most severe they will experience. Reducing dairy, fried, or fatty foods can help ease this symptom in general, as can cutting back on high-fiber foods until the discomfort passes. Over-the-counter medication can break up gas and help it pass through the digestive tract quickly.

man with stomach pain standing in the bathroom



For most who use this supplement, milk thistle will only cause a mild laxative effect. However, diarrhea does affect some people. For those with allergies to plants related to milk thistle, such as ragweed, this side effect is more likely. Antidiarrheal medications containing bismuth can help relieve symptoms.

man rushing to the bathroom because of stomach discomfort



General gut disturbances including bloating may occur in some people who use milk thistle. This possible side effect is temporary as the supplement is often used to treat an upset stomach. Milk thistle has been used for over 2,000 years as a healing herb. Gas relief pills or peppermint tea can help relieve bloating.

older woman experiencing painful bloating on her bed



Indigestion is upper abdominal discomfort that includes bloating, gas, nausea, or feeling too full. Those with known ragweed and other related plant allergies may experience this symptom and other gastrointestinal ones when using milk thistle. To combat indigestion, try adding baking soda to a glass of water to help relieve symptoms quickly.

patient with stomach pain speaking to a doctor



Another possible milk thistle side effect is nausea. This side effect is usually temporary and can be treated the same as nausea from any cause. If the symptom persists through multiple doses of milk thistle, it is best to stop using the supplement and speak to a doctor about an alternative. In general, people can use milk thistle for long periods of time without experiencing any of these side effects.

woman feeling nauseated kneeling in front of the toilet



Although rare, a nosebleed is a possible milk thistle side effect. It's always important to monitor bleeding closely. If the nosebleed does not stop in a few minutes — and the individual doesn't have another issue causing this symptom — seek medical help. Ideally, speak to a doctor before beginning to use any dietary supplement, including milk thistle.

woman with a nosebleed using a tissue



Some users may experience allergic reactions or allergy symptoms when using milk thistle initially. As mentioned, this is especially true for those who are allergic to related plants such as ragweed. Consult with a doctor before starting to use milk thistle if you have known plant allergies. Antihistamine medication can help treat a rash due to allergies.

young woman inspecting a rash on her upper arm



Itching is another possible milk thistle side effect that is often caused by an allergy. Usually, this symptom resolves itself quickly. If it doesn't, discontinue use of the supplement. To help with itching, apply a cold pack or apple cider vinegar to the affected areas.

older man scratching an itchy rash on his arm



When beginning to use milk thistle, some people experience a slight headache. This is one of the most common possible side effects of the supplement and should resolve itself quickly. Drink a lot of water when using any dietary supplement to prevent future headaches.

man at his desk with a headache, in pain


Severe allergic reaction

Anaphylaxis is a severe allergic reaction that can be life-threatening. It causes the immune system to release different chemicals that cause your body to go into shock. Narrow airways, a weak pulse, and low blood pressure are all common symptoms. A person who has experienced anaphylaxis before, or has allergies, asthma, or a white blood cell disorder, should consult a doctor before taking supplements.

woman injecting herself with an epinephrine injector


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