Miliaria: A-to-Z Guide from Diagnosis to Treatment to Prevention

Are heat rashes real? Or is that just an old wives’ tale?

Children’s skin can be quite sensitive to heat. Nursing moms often discover this, especially in the summertime, when their baby’s face turns red where it is against the mother’s skin. This redness comes from blood vessels in the area dilating to cool the skin down. Cooling the skin usually makes the rash disappear within hours, or even sooner. Miliaria is a type of heat rash that lasts for days. It is also a classic newborn rash.

What is it?

Miliaria is a very common skin condition in newborns. The pores of their immature sweat glands plug easily, leading to tiny pink bumps or water blisters.

Who gets it?

Miliaria is most common in the first few weeks of life. It is especially common in hot, humid weather but almost any baby can get it. It is more common in babies who are bundled too warmly.

Older children and adults can also get miliaria, in which case it is often called “prickly heat.”

What are the symptoms?

There are two common types of miliaria. The plugged pores of miliaria crystallina result in pinpoint sweat blisters with no redness. The plugged pores of miliaria rubra (prickly heat) produce small red bumps, with or without sweat blisters.

Either way, miliaria tends to show up on covered parts of the skin, especially where there is friction from clothing. The forehead (under caps or visors), body folds, the upper back and chest, and the arms are the most common locations.

Often prickly heat itches in older children, and they often describe a ‘prickly’ sensation. What newborns feel remains a mystery.

The prickly heat rash can look quite similar to one caused by infected hair follicles (folliculitis), but if you look at the prickly heat bumps with a magnifying glass, no hair follicles will be seen.

An important note: Fever can produce prickly heat, but is not caused by it – if your child has a fever, you still need to find the cause.

Is it contagious?

No

How long does it last?

Miliaria should disappear within 2 or 3 days.

How is it diagnosed?

Miliaria is usually diagnosed based on the physical exam. Sometimes it is confused with other benign conditions such as erythema toxicum. Sometimes it is confused with serious infections, such as herpes. If the diagnosis is not clear, lab tests may be needed.

How is it treated?

A cooler environment, lightweight clothing, and lukewarm baths can be effective in the treatment of miliaria in newborns and in older children.

In older children, prickly heat is treated with gentle cleansing of the skin. I like using Stri-Dex Acne Medicated Sensitive Skin Pads; the salicylic acid helps to unplug the pores.

Hydrocortisone cream (not ointment) can help with itching. Sometimes antihistamines are needed for the itching (and to help with sleep). If the rash becomes infected, antibiotics may also be needed.

How can it be prevented?

Avoiding excess heat and humidity is the best way to prevent miliaria.

Related concepts:

Heat rash, Prickly heat, Sweat blisters