A common cause of diaper rash in infants is the onset of teething. As teething begins, the saliva becomes really acidic in order to lubricate the gums. Some infants spit that saliva out and become like a faucet, and some infants swallow all of that saliva. All the acidic saliva can cause acidic poop, which can cause a diaper rash. It's really important to change the diaper as soon as the poop happens to eliminate how long the poop is next to the skin. It's also really important to use a zinc based cream and layer it on thick. If you put it on in the morning, leave it on until night. It is also helpful to leave a squirt bottle filled with warm water on the changing table. If a bowel movement or a pee happens, you can squirt that off really gently. A wipe can feel like sandpaper on a tushy that has diaper rash.