For adult girls, as their breasts are in the growing stage of size and shape, if the nipples are protruding in underwear, the shape will be changed, such as the nipples being flattened or even sunken into the areola. For adult women, the size and shape of the breasts have been fixed, so it can only be said that the nipples protrude in underwear will be squeezed, or temporary nipple depression, but will not be flattened or cause permanent depression problems.

The dangers of squeezing nipples in underwear
Young girls: Wearing underwear with inappropriate cup sizes and cup spacing can cause nipples to be distorted or sunken into the areola, which can affect breastfeeding inconvenience and hygiene issues later on.

Adult women: Temporary nipple indentations caused by squeezing the nipple in underwear can accumulate dirt or oil and cause discomfort such as itching, eczema or inflammation.