Nipple discharge can occur normally during the last weeks of pregnancy and after childbirth when breast milk is produced. A nipple discharge can also be normal in women who are not pregnant or breastfeeding, especially during the reproductive years. For example, in women, fondling, suckling, irritation from clothing, or sexual arousal can stimulate a nipple discharge, as can stress. However, a nipple discharge in men is always abnormal.
A normal nipple discharge is usually a thin, cloudy, whitish, or almost clear fluid that is not sticky. However, the discharge may be other colors, such as gray, green, yellow, or brown. During pregnancy or breastfeeding, a normal discharge is sometimes slightly bloody. Abnormal discharges vary in appearance depending on the cause. An abnormal discharge may be accompanied by other abnormalities, such as dimpled skin, swelling, redness, crusting, sores, and a retracted nipple. (A nipple is retracted if it pulls inward and does not return to its normal position when it is stimulated.) If a discharge from only one breast occurs on its own (without any stimulation of the nipple), it may be abnormal.