Is it permissible to dye ones hair black?

In the Name of Allah, the Most Gracious, the Most Merciful.

As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh

Pure black dye is not permissible for men and women.

Rasulullah (Sallallaahu ῾alayhi Wasallam) said,

“There will be people who will come later (in my Ummah) and apply black dye like the black colour of the stomachs of pigeons. They will not even smell the fragrance of paradise.” (Sunan Abu Daawūd, vol.2, Pg.222)

To dye the hair any other colour besides black e.g. henna is permissible on condition that it is not the habit of sinful and immoral people. If it is a norm of immoral and sinful people (Fussaq and Fujjar) to dye their hair with a specific colour or one intends to follow modern fashion trends, then it is not permissible to use that colour. Imitating such people is not permissible. (Jawāhirul Fiqh vol2 pg421).

Henna with chemical colours is permissible with the above mentioned conditions.

And Allah Ta’āla Knows Best