The most common thistle used medicinally is milk thistle. Milk thistle has many other names--holy thistle, Mary thistle and silymarin. According to the National Center for Complementary and Alternative Medicine, thistle has a history of thousands of years as a medicinal herb. There are many other varieties of thistle, however--most of which have medicinal uses and few, if any, side effects that are dangerous to man.
Thistle is a general laxative and may cause digestive upset. If used over long periods, it may deplete the body's electrolytes. Careful monitoring of bowels and use of an electrolyte replacement drink helps resolve the situation.
Thistle is a member of the ragweed family and people who have allergies to ragweed will likely experience reactions to thistle. Over-the-counter medications are available to fight allergic reactions. Report severe allergic reaction to your doctor or see a physician in the emergency room if symptoms persist or get worse.
Headache and Irritability
Some users experience headaches and irritability when taking the drug. Mild over-the-counter remedies are enough to counteract the problem.
Rash or Skin Irritation
A few reports of rashes and skin irritations accompany the use of thistle. Discontinue use and report outbreaks to your physician for proper care.
On rare occasions, the use of thistle causes impotence in men. Discontinue the use of thistle if this problem occurs and consult your physician. Usually, stopping the use of thistle alleviates the problem.
Who Should Not Take Thistle?
Any woman who is pregnant, or on a hormone-dependant therapy program should not take products containing thistle. Milk thistle can interfere with estrogen absorption. Milk thistle may also block the effectiveness of oral contraceptives and other birth control. Patients in active treatment for diabetes need to consult their physician before using any products containing thistle as it may decrease the levels of insulin normally required.