Skin tags commonly form on your neck, eyelids, or other places where friction occurs and skin folds exist — for example, on the breasts, groin, or armpits. Skin tags usually start out as soft pinhead bumps when they first appear but may grow larger. Their stem lengths vary, and lesions can range in size from 2 millimeters to 1 centimeter, with some growing up to 5 centimeters. Large skin tags can also cause pain if they burst or a blood clot forms when the stalk gets twisted.