What is the ruling on dyeing hair with chemical dyes, and is it true that they contain an impure substance? What is the ruling on bleaching eyebrows? And how can one get rid of scrupulousness regarding matters of purity?

It is not permissible to dye hair with a substance mixed with impurity, such as alcohol, and washing it suffices. The true nature of chemical dyes is unknown, as is whether they contain alcohol or not. The questioner can check the dye's packaging. Lightening eyebrow hair without plucking from it is permissible, provided there is no deception of a suitor. The cure for obsessive thoughts regarding matters of purity is the knowledge that the default state of things is purity. One does not deviate from this default simply due to doubt and obsessive thoughts; rather, certainty is required.