What would cause melasma in my sister (32) and I (26) about 6 months apart? We both have it on our top lip. : (im sorry... On my sister and i.

Hormones and sun. Melasma is a common problem which is mostly in women. It is related to estrogenic hormones and sun-exposure in women. Treatment needs to be directed to both. Pregnancy and birth control pills are common triggers in women. See your dermatolgist.