Hi D.,
I would get him on an absorbable multivitamin right away. Most body odors are caused by a lack of nutrition (or lack of absorption of nutrition).
Julie's right, it could also be yeast which will effect everything. A probiotic/prebiotic will always help, never hurt, as there is so much sugar in the common eating habits these days. (Avoid yogurt unless it is unsweetened. The tasty ones can help prevent yeast but they won't get rid of it if it already exists.) Even trying to keep the sugars down, it's hard with the breads and french fries and all the other simple carbs. They continue to help breed the yeast.
D., check his tongue and see if there is a white coating. (This is one way a doctor checks for thrush in babies but it works in adults too.) If there is, then his little body is eaten up with it and you need to get proactive. Yeast will break down the immune system over time and causes major diseases to have an opening...
If you want to go this route I can recommend a vitamin and a probiotic that will definitely help.
God bless,
M.