The muhrim (one in ihram) is forbidden to do certain things because of having entered the state of Ihram.
The forbidden things are:
1) Shaving the hair of the head, because Allah says: “… And do not shave your heads until the Hady (animal, i.e. a sheep, a cow, or a camel) reaches the place of sacrifice…” (2:196)
Scholars have added that besides shaving the head, shaving any hair on the body as well as trimming or cutting one’s nails is also prohibited.
2) Using perfume after entering ihram, whether on one’s clothing or body, or in one’s food, or when washing the dead body (muhrim) or in any way whatsoever. The evidence for this being forbidden in ihram is the Hadith of the Prophet (peace be upon him), who said concerning a man whose camel trampled him to death, “Wash him with water and lotus leaves and shroud him in his two garments, but do not cover his head or perfume him with hanoot.” Hanoot is a mixture of perfumes that is usually applied to the dead body.
3) Sexual intercourse, because Allah says: “… So whosoever intends to perform Haj therein (by assuming Ihram), then he should not have sexual relations (with his wife), nor commit sin, nor dispute unjustly during the Haj…” (2:197)
4) Touching one’s wife with desire because this comes under the general meaning of the phrase, “he should not have sexual relations (with his wife),” and because it is not permissible for the muhrim to get married or to propose marriage – so it is more likely that it is also not permissible for him to touch his wife with desire.
5) Killing game (hunting), because Allah says: “O you who believe! Kill not game while you are in a state of Ihram [for Haj or Umrah (pilgrimage)]…” (5:95)
Cutting down trees is not haram for the muhrim, except for those trees within the amyal, i.e., the boundaries of the sanctuary. Cutting these trees is forbidden whether one is in ihram or not. Hence, it is permissible to cut down trees in Arafah even if one is in ihram, because the prohibition on cutting down trees is connected to the Haram (within the sanctuary), not ihram.
6) A prohibition applies exclusively to men is wearing shirts, hooded robes, trousers, turbans, and leather slippers, because the Prophet (peace be upon him) was asked about what the muhrim should wear. He answered, “He should not wear a shirt, hooded robe (burnous), trousers, a turban, or leather slippers.” But he (peace be upon him) made an exception for one who cannot find an izar (lower garment or waist wrapper). Such a person may wear trousers, and one who cannot find sandals may wear leather slippers.
A common perception is that wearing sewn garments means wearing clothes that have stitching in them, but that is not the case. What the scholars meant by that is wearing clothes that are tailored to fit the body or part of it, such as shirts and trousers. Hence, if a person wears a rida (upper garment) or izar (lower garment) with patches on it, that is permissible, but if he wears a woven shirt with no stitching, that is haram.
7) One of the prohibitions of ihram that applies only to women is the niqab, which refers to a veil that covers the face and leaves the eyes uncovered because the Prophet (peace be upon him) forbade that. A similar prohibition applies to the burqa. When a woman enters ihram, she should not wear a niqab or burqa.
With regard to the one who does any of these forbidden things out of forgetfulness or ignorance or because he or she is forced to do so, no expiation is due on them because Allah says: “And there is no sin on you concerning that in which you made a mistake, except in regard to what your hearts deliberately intend. And Allah is Oft-Forgiving, Most Merciful.” (33:5)
Concerning killing game or hunting, Allah says: “O you who believe! Kill not game while you are in a state of Ihram [for Haj or Umrah (pilgrimage)], and whosoever of you kills it intentionally, the penalty is an offering, brought to the Ka’bah, of an eatable animal ( i.e. sheep, goat, cow) equivalent to the one he killed…” (5:95)