This is a skin disease characterized by the loss of pigment, leading to the presentation of white patches. These are highlighted by hyperpigmented areas around the edges in many cases.
Vitiligo occurs in many cases in association with certain diseases including hypothyroidism and pernicious anaemia. Occasionally the body forms antibodies against its own melanin-forming cells but the most common cause is skin fungi. Nutritional deficiencies may cause vitiligo, especially in children.
If no underlying condition is found, then preventing this disease process is unlikely. The Eastern philosophies consider the loss of normal colour in skin or hair to be an indication of a profound lack of vital force. I am not sure if this is a fair assumption because most prematurely grey individuals do not seem to fare worse in longevity or health stakes than others. Without underlying disease vitiligo is not likely to cause long-term health problems in other areas.
Take a multi-B complex supplement at four times the recommended dose for one week and then twice the recommended amount for a further month.
Beta-carotene supplements should be taken twice a day for one week and then daily for three months. At this level yellowing of the skin is not likely but if there is any suggestion, or if pregnant, reduce the dosage by half.
Hair, sweat and blood analysis should be undertaken to assess mineral deficiencies, which should be corrected by taking twice the daily recommended dose for one month.
Any deficiencies should lead the individual to a nutritionist to discuss whether their diet is poor or their absorptive capacity weak. Digestive enzymes may be required but this really should be determined by a professional.
Any underlying condition must be treated.
Topical antifungal creams should be tried. Naturopathic ointments may be recommended but in my experience do not show good results.
Xanthelasma may be a reflection of lipid levels, so triglyceride and cholesterol blood levels are worth measuring.
Review the diet and reduce fat intake.
Ensure that good hydration is encouraged by drinking at least half a pint of water per foot of height and double that if xanthelasma has formed.
Application of Arnica-based creams may help break down the stores and in severe cases laser therapy may be available.
The homeopathic remedy Calcarea carbonica taken at potency 6 taken twice a day for two weeks and repeated in one month if no effect is forthcoming is recommended by one source.
Consult a complementary medical practitioner for an overview of your constitution, which may be showing a tendency to retention.