Yep.. i think its a pretty common thing with babies. Both Jesse and Keira had/have it. Its the same with their hands. Smelly due to the dark warm and wet area. Not much you can really do until they start to sit up really. Milk, dribble and even sweat will just build up over the day.. all you can do is just wipe it with a wet cloth, or i use a baby wipe, as it leaves them smelling nice