The eminent Muslim scholar, Sheikh `Atiyyah Saqr, former head of Al-Azhar Fatwa Committee states that: “If a woman works as a hairstylist or a make-up artist for women, there will be nothing wrong on this so long it is done far from the eyes of men. Non-Maharem men are not allowed to be there. So hairstyle or hairdressing is something allowed in Islam unless the person employed to do this knows that the woman in question wants to apply cosmetics or do such and such so as to appear before strange men (non-Maharem) in which case, the act becomes impermissible for it will involve in helping a person in disobeying Allah.
It should be stressed that a woman is not allowed to work as a hairdresser for men or vice versa, for such a work involves looking to `Awrah (private parts) of opposite sex. The Prophet, peace and blessings be upon him, is reported to have said: “The eyes commit Zina (adultery). Their Zina is gazing (at what Allah has prohibited) A hand commits Zina, its Zina is touching (what Allah has prohibited).”
In conclusion, it should be stressed that a good Muslim or Muslimah cares much for making his or her earning pure. In his Hadith to Sa`d ibn Abi Waqqas, the Prophet, peace and blessings be upon him, said: “O Sa`d! Make your food clean (gained through lawful means) so that your supplication be accepted.”
Almighty Allah knows best.