A skin tag is a small, brown or flesh-colored flap of skin that is usually narrow at its base. Skin tags may appear around the neck, under the arms, under the breasts, in groin creases, and on the inside of the upper thigh area.
There is no known reason for the appearance of skin tags. Skin tags occur most frequently at sites where the skin is rubbed by clothing or other body parts. They tend to show up in hot, moist body creases.
The cause of skin tags are unknown, but they do occur more often on skin surfaces that are hot, moist, or frequently rubbed.