By the will of Allaah, I will perform the obligation of Hajj. I will leave my house in a state of ihram (ritual consecration) and perform ‘Umrah. Is it permissible for me to remain in the state of Ihram till I perform Hajj? Is it permissible to comb my hair and bathe?

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.

There are three patterns of Hajj: Tamattu‘, Qiran, and Ifrad. In Tamattu‘, the pilgrim assumes Ihram for ‘Umrah during the months of Hajj and then ends the state of Ihram after performing ‘Umrah and stays in Mecca until he assumes Ihram for Hajj in the same year.

In Qiran, the pilgrim combines ‘Umrah and Hajj in one Ihram and does not end the state of ihram until he has finished the rituals of Hajj.

In Ifrad, the pilgrim assumes Ihram for Hajj only and does not end his Ihram until he has finished the rituals of Hajj.

Accordingly, if you want to perform ‘Umrah first, then this is Tamattu‘, in which you should end the state of Ihram after performing the ‘Umrah. This step is a requirement in order for Hajj to be Tamattu'. However, if you do not want to end your Ihram, you may do so, yet you have to intend the pattern of Qiran or Ifrad, as previously explained.

As for the ruling on whether a person in a state of Ihram may comb the hair of his head and the like and wash his body, with no perfume involved, then this is permissible. But, if he knows that combing his hair or scratching the scalp will cause hair-falling, then it is impermissible. In Kashshaf Al-Qina‘, the erudite scholar Al-Buhooti said, "If he pours water through his beard or combs it or pours water through his hair or combs it and this results in the fall of dead hair, then nothing is due upon him according to explicit texts."

Imaam Ahmad said:

If a person in a state of ihram pours water through his beard and this results in the fall of dead hair from it, then nothing is due upon him. But if he is certain that the hair that fell as a result of him pouring water through his beard or combing it is living hair, then he is required to offer a ransom.

This is quoted from the words of Al-Buhooti with adaptation.  

Allaah Knows best.