There have been various photosensitizers used to treat vitiligo. Most of them are psoralen sources, but coumarin sources can also be used as they are also phososensitive. Basically these compounds make the skin cells more photosensitive, which is why you have to careful using them if you are in the sun a lot.

Some examples of photosensitizers include dong quai (angelica root), psoralea, parsley, sweet clover, lomatium, and bergamot oil. There is another herb commonly used in the Middle East for vitiligo through the same mechanism, but I cannot remember the name. I have not looked in to it for about 15 years. Anyway, these extracts are applied to the skin then the skin is slowly exposed to the sun to stimulate melanin formation. Of course this is done either after the autoimmunity is addressed or in this case they are also adding immune modulating herbs to their formula. Several of the herbs they are using I have never worked with, so I cannot tell you how effective it is likely to be.