Is it permissible for the pilgrim to remain in a state of ihram from Umrah until Hajj, and is it permissible for him to comb his hair and bathe during the period of ihram?

The types of Hajj rituals are three: Tamattu', Qiran, and Ifrad. Tamattu' is entering into a state of ihram for Umrah during therah of Hajj, then desacralizing (tahallul), and staying in Mecca until entering into ihram for Hajj in the same year. Qiran is combining Umrah and Hajj in a single ihram, and tahallul occurs after completing the rituals of Hajj. As for Ifrad, it is entering into ihram for Hajj only, and tahallul occurs after completing the rituals of Hajj.

If you intend to perform Umrah first, this is Tamattu', and tahallul is obligatory thereafter. If you do not wish to perform tahallul, you may do so with the intention of Qiran or Ifrad.

It is permissible for a person in ihram to comb their hair or wash their body with something that does not contain perfume, unless it is known that combing or scratching will cause hair to fall out, in which case it is forbidden. Al-Buhuti said: "If he passes his fingers through his beard or combs it, or passes his fingers through his head or combs it, and dead hair falls out, there is no penalty according to the clear texts." However, if it is certain that the fallen hair is live, then a fidyah (expiatory sacrifice) is obligatory.