Sheikh `Abd Allah al-Suhaybânî, professor at al-Imâm University, al-Qasîm branch
The ruling on wearing a wig depends on a number of factors.
1. Wigs are unlawful when they are made of human hair and are unnecessary – meaning that they are used simply for beatification and normal cosmetic purposes.
The Prophet (peace be upon him) said: “Allah has cursed the woman who adds hair extensions and the woman who asks for it to be done.” [Sahîh al-Bukhârî (5934) and Sahîh Muslim (2122)]
2. Wigs made of human hair are permitted when there is a real need for them, like if a woman's hair falls out all of the sudden or if she is naturally bald. In this case, she is covering up a substantial and abnormal blemish in her appearance.
The permissibility for this can be gleaned from the permission the Prophet (peace be upon him) gave to `Arfajah b. Sa`d to wear a gold nose after his real nose was cut off in battle. [Sunan Abî Dâwûd (3696) – authenticated by al-Albânî in al-Silsilah al-Sahîhah (1865)]
3. Wigs that are made from other than human hair are another matter. Should they be given the same ruling as human hair wigs, or should they be treated like any other object used for adornment and therefore come under the general permissibility of wearing attractive things?
The clearest opinion expressed by the scholars on this matter is that wigs made from other than human hair are permissible. A woman may wear them as long as she is not seeking to engage in an act of deception. This is the view of the scholars who regard the prohibition of hair extensions to stem from an intention on the part of the woman to deceive a prospective spouse.
This is seen in the narration of Mu`âwiyah where the Prophet (peace be upon him) called the use of hair extensions a "deceit". [Sahîh al-Bukhârî (3229)]
Further evidence for this is found in the hadîth of Asmâ' bint Abî Bakr who narrates that a woman came to the Prophet (peace be upon him) and said: "O Messenger of Allah! I just got my daughter married, and suddenly she was stricken with something that caused her to lose a lot of her hair. Her husband is calling upon me to send her to him. Should I weave extensions into her hair?"
In reply, the Prophet (peace be upon him) rebuked the one who adds hair extensions and the one who has it done for her." [Sahîh al-Bukhârî (5479) and Sahîh Muslim (3962)]
The jurists use this hadîth as evidence that the reason why the prophet (peace be upon him) prohibited the hair extensions is that they were being used to deceive the husband about the true appearance of the girl. She was seeking to hide a defect in the girl's appearance from her husband until after he consummated the marriage.
Certainly, when a wig is worn in order to cause such a deception, it is unlawful, regardless of whether it is made of human hair, other natural hair, or synthetic material. However, when no deception is involved, and the husband knows full well that his wife is wearing a wig to make her more attractive, then this is permissible.
She should make sure that the wig is not made of any impure material, and she should not have any bad intention for wearing it, like trying to look like a man or trying to approximate the specific garb of a certain religious denomination.
And Allah knows best.
Source: Islam Today