18-year-old nipple does not come out is mainly considered to be nipple inversion, caused by nipple inversion there are two kinds of cases: First, in the adolescent development period, due to wearing inappropriate underwear, resulting in long-term pressure on the nipple, nipple inversion, should be replaced with loose, air permeable, cotton underwear, while the hand hand to pull the nipple, to strengthen the elasticity of the nipple support structure, can make nipple to restore the normal shape. Second, congenital factors, mostly refers to nipple dysplasia, mainly caused by the congenital lack of supportive force of the nipple, which requires surgical treatment, and the surgical method is mainly nipple plasty. If physiological factors are excluded, you should go to the breast surgery department or plastic surgery department of regular hospitals in time, and decide whether to have surgical treatment or not after full assessment by specialized doctors. In daily life, we should avoid wearing too tight underwear and moderate breast massage to promote nipple development.