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Baby Heat Rash

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Photo: Wix

What is baby heat rash?

Baby heat rash is referred to medically as miliaria. It is a blockage of the sweat ducts that leads to sweat entering the superficial layers of the epidermis giving the appearance of pinpoint vesicles, pustules, or simply reddish bumps.

It can happen in both adults and infants, even neonates.

The common theme for most cases of miliaria is increased body heat and sweating. When there is difficulty cooling off due to the environment, there can be a predisposition towards noticing this development.

What are the symptoms of baby heat rash?

In neonates, miliaria can be in the most superficial layers of the skin giving the appearance of water droplets on the skin. This is referred to as miliaria crystallina. The surface of these vesicles is thin and easily sheered. In early cases, there is not an inflammatory response so the presence of erythema or redness tends to be absent. Miliaria rubra is a more common appearance that occurs in areas where the skin rubs, such as between the legs, between the skin folds, and under the arms. With blocked eccrine or sweat ducts, the sweat, heat, and friction of the folds can inflame the skin making it appear red or irritated.

What causes baby heat rash?

Baby heat rash in particular tends to come from excess heat and humidity that can build up in the skin folds. Friction and minimal movement can aggravate the condition.

How can I treat baby heat rash?

If there is no inflammation, signs of infection, or discomfort, most cases of miliaria self resolve. Keeping the skin moisturized, using breathable textiles, and maintaining a cooler ambient temperature can benefit treatment and prevention. If there is evidence of inflammation or infection, then discussing the potential need for topical steroids or antibiotics may be necessary.

When should parents seek the help of a doctor for heat rash?

Evidence of discomfort- itching, sensitivity, raw areas, pustules, or other signs of inflammation or infection warrant a visit to your doctor.



What are some rashes that look similar to heat rash? Which of these are serious? What are associated symptoms?

For infants in particular the differential diagnosis for miliaria includes viral exanthems, folliculitis, erythema toxicum neonatorum, candidiasis, herpes simplex, varicella, and neonatal acne. Presence of fevers or other systemic symptoms must be taken into consideration as they may warrant a sepsis workup depending on the age of the infant.

Conditions that can be confused with baby heat rash:
  • Contact dermatitis. Contact dermatitis will present with background erythema or redness along with evidence of peeling, scaling, and small vesicles or blisters. It is often “geometric” with patterns that reflect the point of contact with the product that led to the reaction.

  • Eczema. Eczema in infants tends to favor the areas that they can rub or scratch easily- outer arms or elbows, legs, and cheeks. I often tell parents that if your infant appears to be “snuggling” by rubbing their face on you, they may just be using you as a scratch post:)

  • Folliculitis. Folliculitis is, as the name suggests, inflammation based around hair follicles. When looking the individual pustules, a hair follicle should also be present. This is in distinction to heat rash which is based around a sweat duct which are different from hair follicles.

  • Post-viral rash. Post viral rashes can be difficult to distinguish from heat rash at times. There tends to be background erythema or redness with pinpoint papules throughout. These can be distributed over the torso, arms and legs. These papules are usually not pustules however.

  • Herpes simplex. The classic description of herpes simplex is “dew drops on a rose petal”. This refers to pustules or vesicles grouped together on a reddish erythematous patch or plaque. In neonates these can be diffuse, over the body and include the lips and mucosal surfaces if severe. There is also the risk of systemic symptoms such as fever, lethargy, respiratory distress, and seizures. In neonates it presents in the 1st to 3rd week of life and transmitted during delivery.

  • Neonatal acne. Neonatal acne tends to present on the cheeks, forehead, and chin primarily as pustules or red bumps. This tends to show in the neonates during weeks 2 to 6 of life.

  • Erythema Toxicum Neonatorum (ETN): This is the most common pustular rash of the neonatal period. These starts as red macules or patches that turn into pustules by the 2nd or 3rd day of life. In distinction to the rashes above, it appears in the first week of life.

  • Transient neonatal pustular melanosis: This is a transient rash that does not have the reddish background of ETN but does have the pustules that quickly rupture and leave behind pigmented macules that gradually fade.

  • Seborrheic dermatitis: Greasy scales on the scalp and folds that can appear red and raw in friction and heat bearing areas.

  • Diaper rash: This occurs in the diaper distribution and can develop satellite pustules if secondarily infected with yeast.


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