Is dyeing with henna which women do considered of the apparent adornment? Is it prohibited? Is a woman permitted to use henna during menstruation?

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.

It is permissible for a woman to apply henna to her hands, rather, she is enjoined to do so. It was narrated that the Prophet, sallallaahu ‘alayhi wa sallam, entered upon a woman and said to her: "Apply henna (to your hands). One of you abandons henna until her hand becomes like that of a man." [Ahmad]

Later, that woman did not abandon the use of henna until she died. Even, she used to use henna while she was eighty years old.

Dyeing with henna and other similar forms of adornments must not be exposed before non-Mahram (marriageable) men. It is included in the general forbiddance reported in the verse where Allaah Almighty says (what means): {And not expose their adornment…} [Quran 24: 31] 

It is possible to hide this adornment by using gloves when needed. It is also permissible to use henna during menstruation, post-partum bleeding or any other condition.

Allaah Knows best.