Ref. No. 2468/45-3762
In the name of Allah the most Gracious the most Merciful
The answer to your question is as followed
In some hadiths, it is proven that the prophet of Allah (saws) sometimes used henna on his head and beard for the purpose of receiving treatment or cold from the same. The prophet of Allah (saws) has also urged men to apply henna on their beards and women on their hands. A hadith says: The best thing you change gray hair with is henna and katam (Fath-al-Bari 13/418 – 5899)
And Allah knows the best
Darul Ifta
Darul Uloom Waqf Deoband