Rashes are one of the most common reasons parents contact health professionals in the first years of a child's life, and for good reason: a rash that looks alarming may be completely benign, while one that seems mild can occasionally indicate something serious. The key is knowing which features distinguish one from the other.
This guide covers the most common rashes in babies and young children, how to identify them, and — most importantly — the specific signs that indicate a rash requires urgent medical attention.
Photographing and logging rash observations in Healthbooq — when it appeared, where it started, how it has spread, and any associated symptoms — gives your GP or health visitor the most complete picture of what the rash has done over time.
The Glass Test: The Most Important Thing to Know
Before covering individual rashes, the most important piece of rash knowledge for any parent is the glass test for meningococcal disease. Press a clear glass firmly against the rash: if the rash fades (blanches) under the pressure, it is blanching and less likely to be meningococcal. If the rash does not fade — if the red or purple spots remain visible through the glass — it is non-blanching, and combined with a sick child, this is a medical emergency. Call 999 immediately.
Meningococcal disease causes a petechial or purpuric rash (pinpoint red or purple spots or larger bruise-like patches) that does not blanch because it represents bleeding under the skin. The child is typically very unwell: high fever, rigid neck, photophobia (aversion to light), severe headache in older children, and in babies extreme irritability, high-pitched moaning cry, bulging fontanelle, and dislike of being handled.
The glass test should be performed on any rash in a child who appears significantly unwell, regardless of how the rash looks initially.
Nappy Rash
Nappy rash — contact dermatitis caused by prolonged exposure to urine and stool — appears as redness in the nappy area, usually affecting the convex surfaces (buttocks, inner thighs, genitals) but not the skin folds (which would suggest a different cause). It improves with frequent nappy changes, air time, and application of a thick zinc oxide barrier cream.
A nappy rash that involves the skin folds as well as the convex surfaces, has a bright red scalloped edge, or has satellite spots beyond the main rash is likely to have a secondary Candida (thrush) infection and needs antifungal cream in addition to barrier cream.
Heat Rash (Miliaria)
Heat rash appears as tiny red spots or clear fluid-filled vesicles, usually on the neck, chest, face, or body where sweat cannot evaporate freely. It occurs when sweat glands become blocked — typically in hot weather or when a baby is overdressed. It is not itchy, resolves quickly when the baby is cooled and appropriate clothing is used, and needs no treatment.
Roseola (Sixth Disease)
Roseola is caused by human herpesvirus 6 and follows a characteristic pattern: several days of high fever (often 39–40°C) with a relatively well-looking child, followed by the sudden appearance of a pink flat rash on the trunk as the fever breaks. The rash lasts one to two days and fades. A child who seemed very hot but relatively well for several days and then develops a rash as the temperature normalises almost certainly has roseola. The rash itself needs no treatment.
Slapped Cheek (Fifth Disease, Parvovirus B19)
Slapped cheek disease causes a distinctive bright red rash on the cheeks, often with a pale area around the mouth that accentuates the contrast. A lacy, reticular (net-like) rash then spreads to the body and limbs. The child is usually mildly unwell and the rash resolves within one to two weeks. Importantly, parvovirus B19 can cause significant complications in pregnant women (particularly in the first twenty weeks); anyone who is pregnant and has been in contact with a confirmed case should discuss with their midwife.
Hand, Foot and Mouth Disease
Caused by coxsackievirus, hand, foot and mouth disease produces small grey-white blisters on the palms, soles, and inside the mouth, sometimes with a non-blistering rash on the buttocks and legs. It causes mouth pain (which can affect feeding and cause drooling) and is highly contagious. It resolves in seven to ten days. Paracetamol or ibuprofen for mouth pain; cold foods (ice lollies, cold yoghurt) can also provide relief.
Chickenpox
Chickenpox appears as crops of itchy red spots that quickly develop a fluid-filled blister centre, then crust over. Spots appear in successive crops over three to five days, so a chickenpox rash at any point has spots at different stages of development. The illness is typically more significant in adolescents and adults than in young children; complications in children are uncommon. Calamine lotion, antihistamine, and cool baths provide symptomatic relief. Children with chickenpox should not attend nursery or school until all spots have crusted over.
Key Takeaways
Most rashes in babies and young children are viral and self-limiting, require no treatment, and resolve within days to two weeks. The rash that most urgently needs to be distinguished from benign rashes is meningococcal disease, identified by a non-blanching rash (one that does not fade when pressed with a glass) combined with a child who is very unwell. Performing the glass test on any rash in a sick child takes seconds and provides critical information. Other important rashes include hand, foot and mouth disease, roseola, slapped cheek, chickenpox, and heat rash — each with distinct features.
