In naturopathic school, we're taught that when we have skin issues, the first place to look is the digestive system.
My first suggestion, based on the minimal stuff you have described, is to look for gluten intolerance. Your client can order their own lab from www.enterolab.com
. I'd suggest the gluten stool test at minimum, and adding in the dairy/yeast/egg/soy portions if they are willing. Getting irritants out of the diet will help the most in the beginning. Feel free to Google "celiac vitiligo" or "gluten vitiligo" to find your client info on this.
A good solid dosing of probiotics can only help in this area as well. Feel free to have this person contact me (or look through my store) if they would like to get what I recommend.
A good CLO will always be of benefit, I can also help there.