A man is forbidden to wear even one garment worn by women, even though he can be recognized as a male by his other garments.¹ (Orach Chaim 696:8) says that it is customary to dress in this way on Purim for merry making. Mishna Berurah 596:30—Be’er Hagolah—Taz—Bach say that this custom should be abolished. Likewise a woman is forbidden to wear even one garment worn by men. Not only are feminine garments forbidden to men, but also every ornament and all toiletries and cosmetics that are used exclusively by women, of that region, are forbidden to a man for purposes of adornment or enhancement. Likewise, everything used exclusively by men, is forbidden for use by a woman.

footnotes: ¹ Ramah

A man is forbidden to remove the hair from his armpits and the genital area, even with a pair of scissors when it is cut close to the skin, if it appears that it was done with a razor, for this is the custom of women. It is forbidden to rub the hairs of the armpits or of the genital area with the hands, so that they should fall out, but it is permitted when done with a garment. One who has scabs in his armpits, or in the genital area, and the hair causes him discomfort, is allowed to remove them.

A man is forbidden to pick even one white hair from among the black ones, for this is the way women beautify themselves, and is forbidden because of the enjoinder that "A man shall not wear (a woman's garment)."² 22:5. It is also forbidden to dye even one white hair to make it black. A man is also forbidden to look into a mirror. However, if you look into it for medical purposes, or when you are cutting your own hair, or wish to remove stains from your face, or remove feathers from your head, it is permitted (to use a mirror). In a region where it is customary for men, to look into mirrors, it is permissible for any reason.

footnotes: ² Deuteronomy