Heat Rash or Prickly Heat (Miliaria Rubra)

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Overview

Heat rash (miliaria rubra) is a skin condition also sometimes known as prickly heat. As the name suggests, heat rash is usually found in hot or humid climates or when the body becomes hot, such as during a fever. The condition is caused by blockage of tiny sweat ducts, resulting in small itchy or prickly bumps.

Who's at risk?

Anyone can get heat rash, although it is more common in people who are sweating more than usual (such as someone who has recently moved to a hot or humid location) and less common in certain races of people who are genetically predisposed to sweat less.

Signs and Symptoms

Heat rash can occur after exposure to hot conditions. There can be many small, red bumps all over the body. Heat rash usually occurs in highest concentration in covered areas where there is a lot of friction, such as the neck, chest, and body folds. The face, palms, and soles are generally not affected. Heat rash can cause intense itching and stinging, which can become worsened by heat. The person affected by heat rash may feel fatigued and become intolerant of heat, due to little or no sweating at the affected areas.

Self-Care Guidelines

Prevention and treatment of heat rash consist of controlling heat and humidity. Acetaminophen or ibuprofen can help to reduce fever. Remove any occlusive clothing, limit activity, and seek air conditioning or any cooler environment. Cool compresses can also help with the discomfort. Heat rash usually resolves once people move to a cooler environment. Make sure to drink lots of fluids.

For those with a history of heat rash, consider daily showering with soap and application of topical anhydrous lanolin before exercise.

When to Seek Medical Care

The most common complications caused by heat rash are secondary infection from scratching and heat exhaustion.

Infected areas of heat rash may need antibiotics. Seek care if the area develops pus, redness, crusting, swelling, or tenderness.

In cases of heat exhaustion, the skin will appear hot and flushed without any sweat. The person may complain of dizziness, nausea, weakness, headache, confusion, or difficulty breathing. Heat exhaustion can progress to heat stroke, so medical care should be obtained right away. Symptoms of heat stroke include a very high temperature of 105°F or greater, decreased or loss of consciousness, or seizure.

While awaiting medical care, get the affected person indoors or under shade, undress them, and apply cool compresses to the body. Do not give fluids.

Treatments Your Physician May Prescribe

If there are signs of bacterial skin infection caused by the heat rash, oral or topical antibiotics may be given.

Dehydration may be treated with intravenous fluids, especially if there is vomiting. Heat stroke is treated by trying to quickly reduce the core temperature to normal. Immersion, evaporative, or invasive cooling techniques may be used in addition to rapid administration of intravenous fluids.

Trusted Links

Clinical Information and Differential Diagnosis of Miliaria Rubra

References

Bolognia, Jean L., ed. Dermatology, pp. 510, 578-579. New York: Mosby, 2003.

Wolff, Klaus, ed. Fitzpatrick's Dermatology in General Medicine. 7th ed., p. 730. New York: McGraw-Hill, 2008.