Milk thistle, sold as capsules and tablets, belongs to the same family of plants as ragweed, chrysanthemum, marigold, and daisy. It contains a substance called silymarin, found in the fruit, which is believed to be responsible for any medicinal properties.

So far scientific studies have found no evidence that milk thistle helps in treating hepatitis C.

Milk thistle is generally considered safe to use, but it can have a laxative effect and cause nausea, diarrhea, and bloating in the abdomen. People who are allergic to plants in the same family as milk thistle, such as ragweed, may experience allergic symptoms to milk thistle as well.