WHAT IS LEUCODERMA?
Strictly speaking, Leucoderma is not a medical term, though it has come to mean any white/light coloured skin patch. Very broadly, white patches can be acquired or may be present at birth. Again, both acquired and congenital skin patches can result from hordes of reasons. While congenital patches are not of much importance - since a majority of them are birthmarks anyway, the disease wherein acquired patches develop is generally referred to as Leucoderma (or Leucoderma in medical terms). Other acquired white patches usually follow some preceding disorder.

WHAT CAUSES LEUCODERMA? 
Despite advanced research, medicine is still trying to figure out the exact cause (leave alone the most appropriate treatment!) of Leucoderma. There are numerous theories as to what could cause this disease, of which three have been widely accepted.  The first theory is one of mistaken identity. The immune system mistakes the pigment cells for foreign bodies and destroys them. The second theory states that certain chemical agents destroy the pigment generating cells, while the third theory states that the cells are destroyed due to chemical exposure.  Whatever the cause, the course of the disease is certain - and that is the destruction of pigment cells. But why do only certain areas of the body get affected? Why doesn't this disease affect the entire body? After all, pigment cells are present throughout the body. It's still a mystery. 

IS LEUCODERMA HEREDITARY?
Children of parents where one or both have Leucoderma are only at a fraction of a higher risk than the general population. Even the general population is at a risk of 1-2 %. This means that even with no family history for generations, any normal and fit person too stands a chance of 1-2 % of developing Leucoderma (practically for no reason at all).  

WHAT ARE LEUCODERMA SPOTS WHITE?
White patches need not always spell doom. Only a fraction of them could be the dreaded Leucoderma. And that too, a majority of the cases are amenable to medical management.

Can Leucoderma be caused by consuming contrasting food items like fish/onions with milk?
Nothing can be further from the truth. This is a myth with absolutely no scientific basis. How this old grandma's tale started is still a matter of speculation. A point that should further strengthen the belief that diet has absolutely nothing to do with Leucoderma is that no dietary restrictions of any kind are imposed on a Leucoderma patient. Vitamin-C rich foods, which were once thought to promote the disease process, are no longer restricted either because of their proven and beneficial role as antioxidants.