My 3 Year Old Son Smells Like Onions After Playing/running

My 3 year old son smells like onions after playing/running around. It is hard to get the odor off of his armpits every night in the bath. He drinks V8 Fusion and Organic Milk, eats well and has no rash. He does not like water, so he rarely drinks it. Could this be some kind of milk/dairy allergy? Thank you.