Answered by Shaykh Umer Mian
Question: Assalamu alaykum
Magnesium stearate derived from animals in products such as soaps shampoos is permissible as it undergoes a drastic change.
Does same ruling apply for make-up such as eyeshadow, eyeliner, blusher, foundation. Is magnesium stearate from animals in makeup allowed to be used?
If yes, is prayer valid with such makeup on?
Answer: Wa alaikum as-salam wa rahmatullahi wa barakatuhu
When an impure substance undergoes complete chemical transformation (al-istihalah), the resulting substance is pure. Hence, the resulting substance would be permissible to use (even in prayer) and consume.
According to the Hanafi school of sacred law, an impure substance that undergoes complete chemical transformation (al-istihalah) becomes pure. The following is stated in Maraqi al-Falah, an authoritative manual of sacred law according to the Hanafi school:
الاستحالة تطهر الأعيان النجسة كالميتة إذا صارت ملحا والعذرة ترابا أو رمادا (مراقي الفلاح، باب الأنجاس والطهارة عنها)
“Al-istihalah purifies impure substances such as an animal carcass that transforms into salt or feces that transform into dirt or ash.”
The scholars gave the example of an animal that dies in a salt flat. Initially, the animal carcass is impure, but after sufficient time the carcass may completely dissolve into the salt flat such that no traces of the animal remain. This is complete chemical transformation, and hence the earth at that location is deemed pure. The same could be said for feces that decompose completely, leaving no traces behind. Another classical example is wine that is transformed into vinegar. In this process, the wine undergoes an essential transformation and loses its intoxicating quality. Hence, the resulting vinegar is pure and permissible to consume.
Note that al-istihalah is a type of transformation above and beyond “drastic change.” For example, cooking can produce a drastic change in many types of food (consider how many different ways there are to cook eggs and how different the cooked eggs are from raw eggs), but cooking does not normally result in complete chemical transformation (al-istihalah). Rather, the question is whether a substance has undergone an essential transformation, retaining none of its original properties and being fundamentally altered in its application. When al-istihalah is achieved in this way, the resulting substance is pure, and hence the substance is permissible to use (even in prayer) and consume.
See also this answer.
[Shaykh] Umer Mian