The biggest feature of ladies' underwear is that it is close to the skin and there is no room for storing external genitalia. On the other hand, the front of men's underwear has a raised part for storing male genitals. Men's underwear is generally loose, if it is too tight, it will be bad for genitals, especially for teenagers in the process of growth and development, which will affect normal growth and development.
So men's underwear can be worn by women, but it should be bigger. Ladies' underwear can be worn by men if it is big enough. The reason why men's and women's underwear is different and separated is closely related to the physiological differences between men and women. Although you can wear it, from a health point of view, it is still not recommended that you wear underwear for men and women.