Does milk thistle help with infections? What the research does and doesn't show

No human trial has tested milk thistle for a urinary tract infection, a yeast infection, or any other infection. What exists is two lab-dish studies that found silymarin and silibinin had some antibacterial and antifungal activity against tested microbial strains — a preliminary finding, not evidence that swallowing milk thistle treats an infection in a person.

What the evidence doesn't support

It doesn't support milk thistle, silymarin or silibinin as a treatment for a urinary tract infection, a yeast infection, or any bacterial, fungal or viral infection in a person. No human trial exists for any of these. The lab-dish studies below tested extracts directly against microbes in a dish, at concentrations that don't tell us what reaches the bloodstream or urinary tract after a supplement is swallowed, digested and partly metabolized. Nothing here describes a specific product's dose, and nothing here is a claim about any product.

What the trials found

A 2015 lab study tested silymarin and its main component silibinin against a panel of bacterial and fungal strains in a dish. Silymarin showed antibacterial activity of "little significance" against the bacteria tested, requiring a high concentration (512 µg/mL) to inhibit growth. Silibinin performed better against E. coli specifically, inhibiting growth at a lower concentration (64 µg/mL), and both showed antifungal activity only at a very high concentration (1,024 µg/mL) across the fungal strains tested. The authors describe the results as showing "promising potential," particularly when silymarin or silibinin was combined with an antibacterial drug in the dish, and call for further study — not a claim that either treats an infection in a person.

A 2010 lab screen tested 21 herbal extracts, including milk thistle, against two bacteria linked to gastrointestinal infection: Campylobacter jejuni and Helicobacter pylori. Milk thistle was among the extracts showing the highest growth inhibition of C. jejuni in the dish, but it wasn't among the extracts most active against H. pylori — other herbs (agrimony, goldenseal, meadowsweet, sage) performed better there. Like the study above, this tested extracts directly against bacteria in a lab setting, not milk thistle taken by a person with an infection.

We found no human clinical trial, in either direction, testing milk thistle for a urinary tract infection, a yeast infection, or any other infection.

Questions people ask

Is milk thistle good for a urinary tract infection?

No human trial has tested this. A 2015 lab-dish study found silibinin had some activity against E. coli, a common cause of UTIs, but that's a lab finding at a set concentration, not a test of milk thistle treating a urinary tract infection in a person.

Does milk thistle help with a yeast infection?

No human trial exists for this either. The same 2015 lab-dish study found antifungal activity only at a very high concentration against the candida strains it tested — not evidence that a supplement dose reaches that concentration in the body, and not a test in a person with a yeast infection.

When to talk to a doctor

A suspected urinary tract infection, yeast infection, or any infection with fever, pain or symptoms that persist should be evaluated and treated by a doctor; milk thistle is not a treatment for an infection, and no human research reviewed here supports using it as one. If you're prescribed an antibiotic or antifungal medication, ask a doctor before adding milk thistle — see milk thistle and medications: what to check.

Related reading: milk thistle side effects, milk thistle: what the research does and doesn't show, and what is milk thistle.