Hmm! He's probably just curious about water. Babies use their mouths to explore their world.
By the way, we all absorb products through our skin (and babies do more so). He's probably getting less by sucking on his fingers after dipping them into water with some rinsed-off product in it than he's getting through his skin in the course of a bath.
About the Aveeno products, I'd be leery. Aveeno uses some downright hazardous ingredients in many of their products. You can see at http://www.cosmeticsdatabase.com/wordsearch.php?query=ave...
I try to stick with products rated at 3 or lower. For our daughter's soap, we just use our own, grown-up Kiss My Face olive oil soap (nothing else but that; the olive and chamomile and other combos are not as natural and healthy, but the straight-up olive oil soap is rated at zero, the best possible rating - safer than most "baby" products). It's a huge bar for just a few bucks and lasts a long time. We even use it for her hair. You can see and compare at http://www.cosmeticsdatabase.com/wordsearch_free.php?hq=k...
L.