Ruling on injecting Botox to stop or reduce sweating
Question

What is the ruling on injecting Botox into the hair and armpits to stop or reduce sweating for a period of several months only?
Praise be to Allah.The ruling on this matter depends on two things:
Firstly:
Botox is a toxic substance that is produced by certain bacteria, but it is administered to the patient in very safe amounts.
It says in Mawsoo‘at al-Malik ‘Abdullah li’l-Muhtawa as-Sihhi:
Botox: The botulinum toxin of type A...
This medicine is given by injection in varying doses according to the case. But the cumulative dose should not exceed 200 units during a 30-day period. End quote.
Treatment with toxins, if the amount used is miniscule, does not cause any harm. A number of scholars have stated that it is permissible to use it, especially if it is not of animal origin.
Secondly:
Sweat is one of the waste products excreted by the body, and there is no doubt that any change in the nature of the human body by preventing the operation of any of its functions may expose it to risk and harm.
Hence you should consult trustworthy specialist doctors – not specialists in cosmetics – to find out the extent of harm that could result from using this injection to stop or reduce sweating. The ruling is to be based on the extent of the risk of harm.
Shaykh Muhammad al-Ameen ash-Shinqeeti (may Allah have mercy on him) said:
Regarding what Allah has created on earth for people,
If there is a benefit in it that is not tainted by harm, then according to the scholars it is permissible, unless there is evidence to the contrary, because of the general meaning of the verses (interpretation of the meaning):
{It is He who created for you all of that which is on the earth} [al-Baqarah 2:29]
{And the earth He laid [out] for the creatures} [ar-Rahmaan 55:10].
If there is harm in it and no benefit at all, then it is prohibited, because the Prophet (blessings and peace of Allah be upon him) said: “There should be neither harm nor reciprocating harm.”
If it is beneficial in one way and harmful in another, then there are three scenarios:
1.. The benefit outweighs the harm
2.. The harm outweighs the benefit
3.. The harm and the benefit are equal.
If the harm outweighs the benefit or is equal to it, then it is not allowed, because of the hadith: “There should be neither harm nor reciprocating harm,” and because warding off negative outcomes takes precedence over seeking benefits. If the benefit outweighs the harm, then the scholarly view that is most likely to be correct is that it is permissible, because the established principle is that a greater benefit takes precedence over a lesser harm." (Adwa’ al-Bayaan 7/793-795).
And Allah knows best.