Diaper Rash: Causes, Prevention and When to See a Doctor

The redness appears overnight. Yesterday the skin was fine; this morning there is an angry patch under the diaper and a baby who cries at the wipe.

Almost every parent meets diaper rash in the first year, and almost every parent's first thought is that they did something wrong. Usually they did not. Rash has one main cause, a short list of other causes and a routine that prevents most of it, and none of that is about being a better parent.

Here is what is happening on the skin, what stops it and when to stop treating it at home.

What diaper rash actually is

The American Academy of Pediatrics describes the most common type simply: the diaper area spends much of the day in contact with two very irritating substances, urine and stool. Warm, damp skin under a diaper softens, and the irritants and friction do the rest.

Other causes include a yeast infection, a bacterial infection and an allergic reaction to something in the diaper, the wipes or a cream. The NHS adds diarrhoea, irritating wipes and friction from the nappy itself to the list. Heat and trapped moisture make all of them more likely, which is why Indian summers and the monsoon bring more rash.

How to tell the types apart

Irritant rash is usually pink or red, flat or slightly shiny, on the rounded parts that touch the diaper: bottom, thighs, lower tummy. The groin folds are more protected from urine and stool, so that skin usually looks normal, as the AAP describes it.

A yeast rash looks different. The AAP describes shiny, bright red or pink patches with sharp edges, sometimes with little pink bumps, and usually worse in the groin folds. It is treated differently from irritation, so it needs a doctor rather than barrier cream alone.

An allergic reaction appears where a specific component touches the skin, such as a band under the waistband, and returns each time that product is used. Our guide to diapers for sensitive skin explains how to track one down.

How to prevent diaper rash: five everyday habits

This is the part to remember. Dermatologists and paediatricians agree on the same short list:

• Change as soon as the diaper is wet or soiled. The American Academy of Dermatology puts it first: change every dirty diaper, even if it is just wet, as soon as possible, because moisture inflames skin.
• Clean gently with plain water and a soft cloth, or wipes that are alcohol-free and fragrance-free. Do not scrub. For a sore bottom, a squirt bottle of water is gentler than wiping.
• Dry completely. Pat, then let the air finish the job before the fresh diaper goes on. A damp crease under a new diaper is where the next rash begins.
• Fit loosely enough. The NHS advises against putting nappies on too tightly, because it irritates the skin. Check the size by weight and keep the leg frills turned outward; a diaper that gaps or leaks overnight is usually a fit problem too, as our night leak guide explains.
• Give diaper-free time. The NHS advice is to leave nappies off when possible, because wearing one all the time makes rash more likely.

Diaper rash cream: when and how to use it

A barrier cream sits between skin and moisture. The NHS says a pharmacist may suggest a thin layer at each nappy change to protect the skin; the AAP names zinc oxide and petrolatum as good choices; and for a severe rash the AAD's advice is to layer zinc oxide on thickly, like frosting a cake, and not to wipe it all off at every change.

Use it on clean, dry skin, and follow your own doctor's advice on how much. Our guide to what diaper rash cream is and how to use it settles thick against thin, whether to wipe the old layer off, and what a tube costs per gram. Avoid adding several new products at once. The NHS also advises against soaps, baby lotion, bubble bath and talcum powder in the nappy area. Our guide on whether baby powder is safe for babies sets out what the NHS, Health Canada and the makers themselves say about talc and starch powders. Steroid or antifungal creams are for a diagnosed rash, not for prevention, and only on a doctor's advice.

Extra care in Indian heat and humidity

Hot weather means sweat under the diaper before it is even wet. Keep one light cotton layer over the diaper indoors, skip plastic or waterproof pants, check more often on hot afternoons and let the skin air every day. Our guide to diapers in Indian summer and monsoon has the full routine.

Does the diaper itself matter?

Less than the habits above, but yes. A diaper that pulls liquid away from the surface and keeps it down under pressure leaves skin drier between changes, which our absorbency guide explains. Fragrance-free, lotion-free materials and soft, covered edges matter for babies who react easily.

No diaper prevents rash on its own. A good one buys you a little more dry time between changes, not permission to change less often.

When to see a doctor

The AAP advises contacting your child's doctor if the rash is not going away or is getting worse after two to three days of treatment, or if it includes pimples, peeling skin, blisters, or pus-filled, oozing or crusty sores. The NHS adds: see a health visitor or GP if the rash spreads to other areas, your baby has a high temperature or seems very uncomfortable.

Go promptly if your baby has a fever with the rash, is in significant pain or hard to console. A rash in the creases with spots at the edge, or one that keeps coming back in the same place, also deserves a look, because yeast and allergy need different treatment from simple irritation.

If a rash appears despite all this

The AAD says it plainly: babies have very delicate skin, and sometimes, despite a parent's best effort, diaper rash still occurs. Most mild rash settles within a few days of prompt changes, gentle cleaning and drying.

Keep the routine simple, change one product at a time if you suspect a reaction, and ask for help whenever you are unsure. If you are planning your stock of diapers and wipes, our guide on how many diapers a baby needs per day makes sure prompt changes never run into an empty pack. Before the next pack of wipes, our guide to baby wipes for a newborn shows which two words to find on the ingredient list.

This guide shares general information for parents and is not medical advice. Speak to your baby's doctor about any persistent skin irritation or health concern.