What is the ruling on using alcohol-based perfumes, and do they affect the validity of past prayers?

It is not permissible to use perfumes that contain alcohol, as they are impure and prayer is not valid with them. This is based on Allah Almighty’s saying about intoxicants: "So avoid it" [Al-Ma'idah: 90], which necessitates absolute avoidance. As for previous prayers performed while ignorant of this ruling, they are valid and do not need to be redone.