Color of henna (mehndi) does not invalidate wudhoo and ghusl
26-12-2015 | IslamWeb
Question:
Assalaamu alaykum. I want to apply mehndi (henna) to my hands. However, only chemical mehndi is readily available in the market, and my friend says that wudu (ablution) or ghusl (major ablution) is not right as long I have the color of chemical mehndi on my hands. Is she right?
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad 
is His slave and Messenger.
The mere color of mehndi (henna) does not prevent water from reaching the skin; accordingly the wudhoo is valid when henna is applied to the skin. Please refer to fatwa 83035. We could not find any of the scholars making a distinction between natural and chemical henna in this regard.
The criterion is the absence of any substance that prevents water from reaching the skin. An-Nawawi 
wrote, "There is no harm if the color of henna remained as long as the henna itself is removed (without there being any solid layer left)..." [Al-Majmooʻ]
The Maaliki scholar Al-Hattaab wrote, "There is no harm with the traces of henna (color) on the hand or feet or elsewhere and when performing wudhoo or ghusl such color is not regarded as a part of the skin left without washing, i.e. there is a barrier preventing water from reaching it ..." [Mawaahib Al-Jaleel]
Shaykh Ibn Baaz said in his fataawa titled "Noor ʻala Ad-Darb":
"If the kohl (eyeliner) produces an impermeable layer that prevents water from reaching the skin, then it must be rubbed off and removed. wudhoo and ghusl are invalid in this case because of such film preventing water from reaching the skin. However, if this kohl is a mere coloring that does not prevent water from reaching the skin, such as the color of henna and the like, then there is nothing wrong with it (and wudhoo and ghusl are valid in this case). However, if it produces a layer or film that prevents water from reaching the skin, then it must be removed before performing ablution and ghusl. The same ruling applies to henna; if it produced a layer preventing water from reaching the skin, then it must be removed; otherwise, if it is a mere color and has not produced an impermeable outer film on the skin (then it should not)."
Allaah knows best.