My son had that when he was drinking from a bottle with a latex nipple. Turns out he has a latex allergy. Banana & avocado often go hand in hand with latex allergies. My girls got that rash from drinking fruit juices & citrus fruits.
Stephanie, mom to 3 big girls (10, 13 & 19) & 1 sweet little guy (3)
Mom to my girls ('94), ('99) & ('02)
And my little guy (12/09)