Hair straightening in Islam, is it permissible? [is hair straightening haram in islam; hair straightening islamqa]
Yes! It is permissible to straighten one's hair in Islam.
One thing to keep in mind is that the substance used for straightening the hair should not stop water from getting into the roots of the hair while having ghusl.
In case of wudu, If the substance used for straightening the hair makes an impermeable layer on the hair then it does not mean that wudu is invalid, because the requirement of wiping the head in wudu is not strict, and what is required is to wipe the head only, not to wash it.
Another thing to keep in mind is it is essential to pay attention to avoiding extravagance, and to not straight with the intention to attract non-mahrams and to be beware of using anything that may be harmful, even if the harm it may cause may not be obvious immediately.
And Allah knows best!
