The use of henna has been found in Islam and has been practiced by Muslims for centuries. The Prophet Muhammad 
has many authentic sayings concerning henna. Authentic sayings of Prophet Muhammad are called hadith. Second to the Qu’ran, hadith are taken as evidence, that Muslims abide by, to lead their lives as God (Allah), wants them to. In many ahadith we find the benefits and beauty of using henna. We also find many Scholars of Islam such as Ibn Qayyiym Al-Jawziyya mentioning henna several times in his book “Medicine of the Prophet”. We will now look at what we find in Islam about henna.
As for its use as a dye, he mentions “Al-Bukhari related in his Sahih, from ‘Uthman b. ‘Abd-Allah b. Mawhab: We
went in to Umm Salma, and she brought out for us some of the hair of the Messenger of Allah, and lo, it was dyed with henna and indigo.” (Bukhari, Libas, 66) And in the four sunan, from the Prophet , it is related that he said, ‘The best you can use for changing the color of white hair are henna and katam.’ (Tirmidhi, Libas, 20).In the two books of the Sahih, from Anas, it is quoted that Abu Bakr used hair dye of both henna and katam. (Muslim, Fada’il, 100)” (Ibn Qayyim; 259) (Side note here. What is Katam? It is a plant from Yemen which produces a reddish-black dye).
Henna has medicinal properties as well. Ibn Qayyim says, “When headache is from a burning heat and is not from some substance which must be evacuated, henna has a very evident benefit. When it is pounded and applied to the forehead as a dressing with vinegar, it calms the headache. It contains a power which is appropriate to the nerves; when it is applied as a poultice it calms these pains. This is not specifically for pain in the head but is generally for all the limbs. It has a constringent property whereby the limbs are strengthened, and when applies as a dressing to the
site of the burning inflammation, it calms it.” (Ibn Qayyim; 64) He goes on to state, “Al Bukhari relates, in his History, and Abu Dawud in his sunan, that the Messenger of Allah , if anyone ever complained to him of a pain in the head, would say, ‘Have yourself cupped.’ If anyone complained to him of a pain in the legs, he told them ‘Anoint yourself with
henna’ (Abu Dawud, Tarajjul, 188, 19; Talaq 46).
Among its advantages is that it is a useful dissoluent for burns by fire.
When used as a poultice, it has a power appropriate to the nerves; when
chewed, it is beneficial for ulcers of the mouth and any blisters which
occur in it. It heals thrush which occurs in the mouths of children.
Bandaging with it is beneficial for hot inflammations, and its effect on
abscesses is similar to that of dragon’s blood plant. When its flowers are
mixed with warm wax and rose oil, it is good for pains of the side.
When its flowers are put between the folds of woolen clothing, they scent it
and keep moths away…When fingernails are smeared with henna paste, it
improves and benefits them. When made into a dough with ghee, it can be
used as a dressing for the vestiges of hot inflammation which exude yellow
liquid, and it is beneficial for them…It causes the hair to grow,
strengthens and beautifies it, and strengthens the head. It is good for
blisters and pustules occurring on the legs and feet and the rest of the
body. (Ibn Qayyim; 65)
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