Goldenseal is a potent remedy for disorders affecting mucous membranes of the body, notably of the eye, ear, nose, and throat, the stomach and intestines, and the vagina. As a dilute infusion, goldenseal can be used as an eyewash and as a mouthwash for infected gums. Highly valued as a remedy for psoriasis. Internally, goldenseal increases digestive secretions, astringes the mucous membranes that line the stomach, and checks inflammation. It should not be taken for an extended period of time because it reduces the body's ability to absorb some nutrients; notably, B vitamins. It helps to reduce heavy menstrual bleeding and is used by some midwifes to stop postpartum hemorrhage.

In the past century, very little scientific research has been done on goldenseal. Its major effects are attributed to the alkaloids hydrastine and berberine. In animal experiments, hydrastine lowered blood pressure; berberine stimulated digestion and the secretion of bile, lowered blood pressure, and inhibited growth of bacteria. Berberine gives goldenseal its yellow color and bitter taste.

Fresh goldenseal may cause ulcerations of the skin when applied externally; reports of this reaction relate to homeopathic remedies of the mid nineteenth century which contained jimsonweed and zinc oxide in addition to goldenseal. No recent reports of toxicity occur in the literature. Several books warn pregnant and nursing women and people with heart problems to use goldenseal cautiously, presumably because of the lack of toxicity studies. While it has not been documented scientifically, goldenseal may disrupt intestinal flora; some herbalists therefore recommend taking acidophilus with it.

Goldenseal stimulates the muscles of the uterus and should NOT be taken during pregnancy.