Irritation on neck

Kate

Hello

My 3 mo old has a chubby chin and we notice he gets irritation underneath. It clears up pretty quickly when we put a little aquafor on it. Any tips on how to keep this from happening?

My daycare sent a picture today (see below) and I know his neck didn’t look like that when I washed his face this morning. It just comes out of nowhere.

Help please!