What causes heat rash in babies?

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Last updated: June 26, 2025View editorial policy

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From the Guidelines

Heat rash in babies is primarily caused by overheating, which can be prevented by dressing them appropriately for the environment and avoiding overbundling. When a baby overheats, their immature sweat glands can become clogged, trapping sweat beneath the skin and causing small, red bumps or blisters to form. This commonly occurs in hot, humid weather or when babies are overdressed. According to the American Academy of Pediatrics, infants should be dressed in no more than one layer more than an adult would wear to be comfortable in the same environment 1. To treat heat rash, keep your baby cool by dressing them in lightweight, loose-fitting clothing and maintaining a comfortable room temperature.

  • Avoid using thick ointments or creams that can further block pores.
  • Instead, keep affected areas clean and dry.
  • Cool baths with baking soda (1-2 tablespoons per tub) can provide relief. Most heat rashes resolve within a few days without medical treatment. If the rash persists longer than 3-4 days, worsens, or if your baby develops a fever or seems uncomfortable, consult a healthcare provider. It's essential to note that heat rash occurs more frequently in babies because their sweat glands are still developing and can't efficiently regulate body temperature like adults can, making them more susceptible to overheating and subsequent rash development 1.

From the Research

Causes of Heat Rash in Babies

Heat rash, also known as prickly heat or miliaria, is a common condition that affects babies, especially in warm weather. The main causes of heat rash in babies are:

  • Immature sweat glands: Babies have small, immature sweat glands that are not able to cool the body efficiently, leading to overheating and heat rash 2, 3.
  • Overheating: Babies can easily overheat, especially when dressed in too many layers or exposed to high temperatures, which can cause heat rash 4, 3.
  • Blocked sweat glands: When sweat glands are blocked, sweat can't evaporate and cool the skin, leading to heat rash.

Factors that Contribute to Heat Rash in Babies

Several factors can contribute to the development of heat rash in babies, including:

  • Age: Premature babies are more susceptible to heat rash due to their immature sweat glands 2, 3.
  • Environment: High temperatures and humidity can contribute to heat rash in babies 4, 3.
  • Clothing: Dressing babies in too many layers or clothing that traps heat can increase the risk of heat rash.

Treatment and Prevention of Heat Rash in Babies

While there are no direct studies on the treatment of heat rash in babies, calamine lotion has been shown to be effective in reducing skin irritation in children with cast immobilization 5, 6. To prevent heat rash in babies, it's essential to:

  • Keep them cool: Dress babies in light, breathable clothing and ensure they are in a cool, well-ventilated environment.
  • Monitor temperature: Check the temperature of the environment and adjust clothing accordingly.
  • Avoid overheating: Avoid overdressing babies and ensure they are not exposed to high temperatures for extended periods.

References

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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