I know that a Muslim woman is forbidden from wearing a complete set of makeup, i.e. on the eyes, lips or skin. But what is the ruling if she uses lip balm only?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Using makeup or other cosmetics, such as lip balm, is permissible if the relevant regulations of the religion are observed. One of these conditions is that a woman uses such things only inside her home so that no one sees her besides her husband and Mahram (permanently unmarriageable) men. Another condition is that such things are manufactured from pure materials or impure materials that have transformed into other materials through the manufacturing process. A woman is not permitted to go out with her face adorned with cosmetics unless she is veiled. Otherwise, she is sinful. Allaah Almighty says (what means): {And not expose their adornment except that which [necessarily] appears thereof and to wrap [a portion of] their head covers over their chests and not expose their adornment except to their husbands.} [Quran 24: 31]

Allaah Knows best.