in patches is relatively common. There are many causes of this, some of which are normal and some of which indicate an underlying disease. Regardless, I would suggest your son be evaluated by his primary care physician
. In addition, a dermatologist
(a skin and hair specialist).
In general, hair loss is known medically as alopecia. Hair is actually a complicated organ. Hair follicles go through many phases, some of which are a growth phase and some which are in a resting phase. Alopecia areata is the term the that medically describes hair loss in a specific clump. This can be caused by many reasons.
The most likely cause of what you describe is alopecia secondary to stress. While not fully understood, we know that emotional and physical stress can cause the hair follicles to all go into the resting phase. From this, the hair can then fall out at once. In fact, what you describe of hair loss during a period of stress is common. This can subsequently resolve after the stress passes.
Hair follicles change colors over time. It is possible that losing the younger colored hair follicles has brought out the white hairs.
There are other causes that should be ruled out. These include autoimmune disorders, infections of the skin or endocrine (hormone) disorders.
Talk to a dermatologist.