Ask Dr. Mom: Rash Decisions

Q. My 9-month-old son recently developed a particularly bad diaper rash. I’ve been treating it with the same ointment I have used for him before, but this time it hasn’t helped. My mother says he got the rash because he’s cutting a new tooth. Is this true? What else can I do?

A. Almost every baby experiences one or more bouts of diaper rash before he is potty-trained. It occurs less often in breastfed infants (though we aren’t sure why), and more often in infants.

8 to 12 months of age, probably because their eating habits are changing dramatically at this time. In the past, diaper rash was often blamed on teething (hence your mother’s allegation), but we now know this to be untrue since we have a greater understanding of the conditions that cause this type of rash.

The major culprit is wet skin in the diaper area; when skin stays damp for too long, it becomes more susceptible to damage from chafing and rubbing. And once the skin’s surface is damaged, it is then more easily irritated by the interaction of chemicals, enzymes, and bacteria present in urine and/or feces. Because bowel movements harm the skin more than urine, a case of diarrhea significantly increases a baby’s risk of diaper rash.

Diaper rash is fairly easy to spot. You’ll see red, shiny patches of skin anywhere that’s in direct contact with a wet or soiled diaper  — the lower abdomen, buttocks, genitals, and thigh folds. Many diaper rash episodes are very brief, lasting only a day and resolving themselves without any special treatment. But it can be uncomfortable for your baby, so follow this “A-B-C-D-E” strategy to care for his sensitive skin:

Air-dry skin that’s in contact with the diaper as much as possible. Check your baby’s diaper frequently, and change it as soon as you realize it’s wet or soiled. If you’ve got time, lay him on a towel and leave his diaper off for a while following diaper changes, allowing his skin to dry naturally rather than get further irritated by rubbing. Make sure his bottom is thoroughly dry before putting on a new diaper, and fasten it a tad loosely to allow air to circulate. Try super-absorbent disposable diapers for a few days if you’re not already using them. Older babies who may be sleeping through the night, like your son, should be awakened once to change their diaper until the rash has improved.


Barrier creams will protect your baby’s skin from moisture and the irritating chemicals in urine and feces. The most common ingredients in over-the-counter diaper rash products are zinc oxide and white petrolatum, which provide a soothing, water-impermeable shield and promote healing. This step is especially important if your baby has diarrhea. Don’t try to wash the cream or ointment off at the next diaper change; just gently wipe the surface and apply more protection to the base layer. A thick application is especially needed at night and during naps.

Talcum powder, which was once widely used against diaper rash, is no longer recommended because accidental inhalation can have severe effects, like pneumonia and even death. Today, a cornstarch-based powder is commonly recommended to prevent diaper rash by reducing skin friction. New studies confirm that it does not promote the growth of yeast, as once believed, and it does not pose as much of an inhalation risk as talcum powder.


Clean the diaper area every time you change your baby. If he has a bad rash, avoid using scented diaper wipes, as they may contain fragrances that can irritate damaged skin. Unscented wipes are available, or you can use lukewarm water and a soft cloth. After bowel movements, use a mild soap recommended for babies to remove bacteria left on the skin. Avoid rubbing, as this can cause chafing and further damage. Instead, use a plastic squeeze bottle to direct a gentle stream of warm water that will rinse off stool without scrubbing. Rinse again with warm water to remove all the soap. And don’t forget to wash your own hands before and after diaper changes!


Diapers with absorbent gelling material decrease urine contact with baby’s skin, protecting it from a rash. If you use cloth diapers, presoak those that are heavily soiled and wash them separately from other clothing, using hot water and rinsing twice to remove soap residue. Do not use fabric softeners or antistatic products that can irritate a baby’s skin. To keep your baby drier, buy liners to go inside cloth diapers.


Educate yourself so you’ll know when to call the doctor. If your child’s rash hasn’t improved dramatically after two to three days of standard treatment, a yeast infection is very likely. You should have his pediatrician take a look at it. Yeast readily invades skin that has been damaged by diaper rash. You should suspect a yeast infection if the skin on your baby’s thighs, genitals, or lower abdomen  — including the skin creases  — looks bright red with red dots at the edges.

Be aware that skin damaged by diaper rash is also susceptible to a bacterial infection, posing a serious medical problem, especially in the newborn period. Clues to a bacterial infection in the diaper area include rapid progression of the rash, blisters, pimple-like sores, yellowish oozing areas, red streaks, or boils. Notify your baby’s doctor right away if you see any of these signs or if your baby has a rash and also seems sick.

Other causes of a rash in the diaper area that can be mistaken for ordinary diaper rash are prickly heat, eczema, seborrhea, or even a nutritional deficiency or chronic illness. Your doctor will be able to tell you for sure.