Is working as a sales representative for a cosmetics company (such as Avon and others) permissible or forbidden?

The default ruling is that selling cosmetics is permissible. However, it is forbidden to sell them to someone known to use them for impermissible purposes, such as displaying oneself immodestly to non-mahram (definition) men. It is also forbidden to sell them if their impermissible use is prevalent in society, except to someone known to use them permissibly. Furthermore, it is a condition that they are not mixed with impurities, that their harm is not predominantly assumed, and that they do not bear images of women revealing their charms. As for a woman's work, it is permissible with legitimate Islamic controls, including: avoiding mixing with men, wearing the full hijab (definition), and not traveling except with a mahram.