Re: Bumps on the underside of his belly?
Sounds like insect bites to me, there are a lot of flies around my neck of the woods now, and if it's the same where you are it's a likely diagnosis! (Pictures always help!)
For prevention, just make sure you apply fly spray/gel as thoroughly as possible to make sure you dont leave anywhere vulnerable to bites!
There's all sorts of lotions and potions that people use to soothe lumps and bumps, but if they aren't bothering him then preventing more bites is probably more important than putting anything on the ones he has now.
Make sure to keep an eye on them though, if they get bigger, feel hot, start oozing or bothering him lots then it may mean they are getting infected.
Hope they go down soon!