J.C.
Dear R.,
Alopecia areata is not a fungus... it is an autoimmune disorder. Almost like an allergy. If you want to pursue medical treatment, take your son to a pediatric dermatologist. You can also get more information on the National Alopecia Areata Foundation's website (NAAF) at www.naaf.org... they may even have a list of physicians in the area.
I used to be the director of a foundation that helped children with alopecia. It's a little scary at first, but it's not contagious, it's not medically disabling and it may go away on its own. It also tends to run in families, so you may ask some sibs or in-laws if they ever experienced this kind of hair loss.
Hope this helps!
J. C.