السلام عليكم ورحمة الله وبركاته
1. It is undeniable that this treatment causes the formation of a layer around the hair shaft.
2. Layers formed on areas that must be reached by water during ṭahārah are of two types: permeable, and impermeable to water. The permeable layer does not hinder the validity of wuḍū and ghusl; it is only the impermeable layer that causes an obstruction in this regard.
3. The impermeable layer may be further divided into two sub-categories:
3.1 a layer that has a body (jirm), perceptibly distinct and separate from the skin, and removable from the skin through acts such as scraping or peeling.
3.2 a layer that has been worked into the skin to such an extent that it is no longer has a perceptibly distinct and separable body, although some of its traces remain perceptible.
4. The layer described in 3.2 does NOT hinder the validity of wuḍū and ghusl.
5. Although impermeable to water, the coating formed on the hair by the Brazilian treatment is, in the first place, not of the type that has a visually perceptible body, although its effects are noticeable.
6. Furthermore, this coating forms at the molecular level. Although acknowledged to exist, things at this level do not of necessity have an effect on the aḥkām of the Sharīʿah.
7. Oil applied to hair forms a layer as well. Its effects are visible in the shine, smoothness and slickness that it imparts to the hair. When worked into the hair to the extent that it no longer constitutes a jirm distinct and separate from the hair, it presents no obstacle to the validity of ṭahārah.
8. From the exclusive perspective of obstructing water from reaching the hair, it is our considered view that the Brazilian hair treatment does NOT hinder the validity of ṭahārah.
9. This fatwā focuses on the obstruction angle exclusively. Further factors that might impact upon the Sharʿī status of hair treatment, such as the origin and purity of the ingredients of substances used, have not been considered for the present moment.
10. In no way should the approval of this treatment in terms of obstructing water, permissibility of origin, and purity, be construed to mean that its use in a manner that violates the Sharīʿah is condoned.
والله تعالى أعلم
And Allāh knows best.