Diaper rash: what causes it, what to do, and when to worry

What causes diaper rash

The diaper area is warm, damp and rubbed against, which is a hard combination for skin at any age. Four things cause most rashes:

• Moisture and time. Urine and stool break down the skin’s barrier when they sit against it. This is the cause in most cases and it is why “change more often” is the first advice you will get from anyone.
• Friction. Skin rubbing against a diaper, or against itself in a skin fold, especially once a baby is crawling.
• A change in what goes in. Starting solids, a new food, a course of antibiotics, or a bout of diarrhea all change stool acidity. A rash that appears a day or two after any of these usually has that cause; our guide to solids and antibiotics explains why.
• An irritant or an allergy. Fragrance and alcohol in wipes, a soap or a detergent, or occasionally a material in the diaper itself.

Diaper rash is most common between 9 and 12 months, though it happens at any age in any diapers. It is not a sign that anything has been done wrong.

Which type of rash is it?

Most rashes are the first one on this list. The others matter because they need different treatment, and because a rash that will not clear on a normal routine is usually one of them.

Irritant dermatitis, the ordinary kind

Pink or red, shiny, sore-looking skin on the parts that touch the diaper: buttocks, thighs, genitals. The skin folds and creases are usually spared, because the diaper does not sit in them. This is the one that responds to changes, air and barrier cream.

A yeast (candida) rash

Deep red, often with a slightly raised border, and it does get into the creases. There are often small separate spots just outside the main patch. It commonly follows a course of antibiotics or a rash that has been present for several days. It needs an antifungal treatment, so it is worth a call to your doctor or pharmacist rather than more of the same cream.

A bacterial rash

Bright red patches, sometimes with yellow crusting, pus, small blisters or pimples. Sometimes with a fever. This one needs to be seen.

An allergic or contact reaction

A rash whose shape matches something: a band exactly where the elastic sits, a rectangle where a wipe was used, a line at the waistband. Shape is the clue. If the rash has an edge that looks drawn on, something is touching the skin that should not be.

What to do, in order

This is the routine every major paediatric body recommends, and it works for the great majority of rashes.

1. Change more often

   As soon as the diaper is wet or soiled, not on a schedule. Overnight, change once in the night while the rash is healing if your baby wakes anyway.

2. Clean gently

   Warm water and a soft cloth, or a wipe that is free from alcohol and fragrance. Pat, do not rub. If the skin is very sore, squirt water from a bottle instead of touching it at all.

3. Let it dry

   Air is the part everyone skips and the part that helps most. A few minutes of diaper-free time on a towel at each change, more if you can manage it.

4. Apply a thick barrier

   A cream or paste containing zinc oxide or petrolatum, thick enough that you can still see it. Its job is to keep moisture off the skin while the skin repairs. Apply it at every change. Our guide to barrier creams covers what to look for and how much to use.

5. Leave the barrier on

   You do not need to scrub the cream off at each change. Wipe away the soiling and add more on top. Take it back to bare skin once a day, gently.

6. Loosen the fit

   A slightly looser diaper lets air move. If the diaper is leaving red marks at the thigh or waist, it is too tight regardless of the weight on the pack.

When to call your doctor

Call your paediatrician, family doctor or pharmacist if:

• the rash has not started improving after two to three days of the routine above
• there are blisters, pimples, peeling skin, open sores or anything oozing
• there is pus, or yellow crusting
• your baby has a fever alongside the rash
• the rash is bright red with small spots spreading beyond the main patch, especially during or after antibiotics
• the rash is spreading beyond the diaper area
• your baby seems to be in pain, is not feeding, or is very unsettled
• you are worried. That is a sufficient reason on its own.

Our guide to when to see a doctor sets out which of these need a same-day call, what to bring, and what to expect at the appointment.

How to prevent the next one

• Change promptly. The single most effective thing, and the least interesting.
• Use a diaper that pulls moisture away from the skin, and check the fit. Absorbency is only useful if the wet stays in the core rather than against the skin.
• Keep wipes simple. Fragrance free and alcohol free. A water-based wipe is a reasonable default for reactive skin.
• Barrier cream at the bedtime change, if your baby is prone to rash. The overnight diaper is the longest wear of the day, and our overnight guide covers the bedtime routine.
• Air time daily, even without a rash.
• Watch the transitions. New foods, antibiotics, teething and travel are when rashes appear. Being ready for it is most of prevention.