Hadith 8:1977
Abu Bakr narrated to us, he said: Sharik narrated to us, from Layth, from Mujahid and 'Ata, they both said: There is no harm in the *muhrim* (one in the state of ihram) treating himself with henna. And they disliked that he should dye [his hair or skin] with it.
حدثنا أبو بكر قال حدثنا شريك عن ليث عن مجاهد وعطاء قالا لا باس ان يتداوى المحرم بالحناء وكرها أن يختضب بها