Is it healthy to not wear bra?

There's no medical reason to wear a bra, and not wearing a bra will not impact your health. However, wearing a bra is the best way to reduce breast ptosis. Breast ptosis, or sagging, occurs when the ligaments in the breast lose their elasticity. This is partially caused by genetics, and partially caused by excessive bounce. Bras keep breasts anchored to the body, which minimizes breast bounce.