Answering this question requires some detailed explanation:

First: Extending one’s hair with their own natural hair, whether the person is male or female:

This refers to someone who gathers hair that has fallen out and then uses it to create weaves or extensions for their own hair. This default ruling here is permissible, since they are using a part of themselves, similar to someone using healthy skin to cover a burn. Especially if they have experienced hair loss due to a condition or illness and wish to restore their hair to its previous state.

However, this is only impermissible if the person’s intention is to imitate immoral or indecent people, as this falls under the warning mentioned in the ḥadīth: “Allāh has cursed the woman who makes hair extensions and the one who seeks hair extensions,” because it involves prohibited imitation [of immoral people]. But if it is simply for beautification, or a woman seeking to please her husband or a husband seeking to please his wife, it is allowed.

Second: Using the hair of another human being to extend one’s hair:

Most scholars prohibit this because it involves using parts of another human’s body, which is sacred.

However, Imam Muḥammad ibn al-Ḥasan (may Allāh be pleased with him) allowed it, and this is the opinion we give a fatwā upon. The reasoning is that hair is a renewable part of the body, similar to blood. Just as it is permissible to donate blood in certain cases, it is likewise permissible to donate hair or any renewable part of the body.

Third: Using animal hair for extensions:

In this case, the ruling depends on the type of animal. If it is a ḥalāl (lawful-to eat) animal, like cows, sheep, camels, and similar animals, it is permissible to use their hair with two conditions:

1. No deceit: For instance, if someone (man or woman) deceives another by giving the impression that they naturally have long or thick hair when in fact they do not. This is a form of deception, which is prohibited as Allāh says: “And when you speak, be just.” [Al-᾽An῾ām 6:152], and the Prophet (peace and blessings be upon him) said: “Whoever cheats us is not one of us.” However, if a wife does this for her husband or vice versa, it is not considered deceit.
2. No imitation of immoral and indecent people.

The second type of animal is prohibited ones, such as pigs and dead animals. As for pig hair, the majority of scholars prohibit using it in any form.

The Mālikī school, however, holds that pig hair is pure, so if it is cut with scissors, it is permissible to use, even if the cutting occurs after the pig’s death, because hair is considered something pure regardless of life, and what is pure regardless of life does not become impure upon death. Therefore, it is permissible to use pig hair for hair extensions according to their view, but with the same two previous conditions.

As for hair from a dead animal, we must consider the status of the animal when it was alive. If it was an animal whose meat is permissible to eat and can be ritually slaughtered, it is permissible to use its hair even if the animal dies without being slaughtered. This is the opinion of the majority of the Ḥanafī, Mālikī, and Ḥanbalī schools.

Only the Shāfi῾ī school prohibits this due to their belief that impurity transfers to all parts of the animal after death.

Fourth: Using synthetic hair for extensions:

This is permissible with two conditions:

1. No deceit or misrepresentation to others.
2. No imitation of immoral or indecent people.

It is also important to note that synthetic hair attached to a woman’s natural hair does not serve as a substitute for a head covering. Since it is attached to her hair, it takes the same ruling as the hair itself, including the permissibility of wiping over it during wuḍū᾽. Therefore, it must be covered with a ḥijāb.

Based on these guidelines, it is permissible for our 16-year-old daughter to use hair extensions, provided the above conditions are met.