how old is your son?
HFMD is very contagious, but it is rarely life threatening, just that it causes much discomfort in your child, due to the ulcers and blisters.
my girl got it twice before.
she was running a fever for a few days, a few ulcers and a loss of appetite.
took her about 5 days to recover. most impt is to keep them hydrated and make sure they clean and wash their hands frequently.