How Long Do Heat Rashes Last?

Reviewed on 4/12/2022
Newborn baby with heat rash
Heat rashes usually go away on their own within a few days and should be treated by a doctor when they do not.

Heat rash (also called sweat rash, prickly heat, or miliaria) is a type of heat-related illness that describes red bumps that form when sweat ducts become blocked. 

Heat rashes usually go away on their own within a few days. If the heat rash does not go away within 3 to 4 days, see a doctor. 

What Are Symptoms of Heat Rashes?

Symptoms of heat rashes include:

  • Small, raised spots on the skin
  • May look like a cluster of tiny bubbles under the skin or like a cluster of small pimples
  • An itchy, prickly feeling
  • Mild swelling
  • Skin irritation
  • Skin redness (less obvious on brown or black skin)
  • Rash often appears on the head, neck, chest, or anywhere where the skin rubs together (such as an armpit)

See a doctor if you have a heat rash and symptoms of other heat-related illness including heat exhaustion or heat stroke (a medical emergency) such as: 

What Causes Heat Rashes?

Causes of heat rashes include:

  • Clogged sweat ducts that cause perspiration to become trapped under the skin
  • Underdeveloped sweat ducts
  • Hot, humid weather or tropical climates
  • Intense physical activity that causes excessive sweating
  • Overheating

Babies and young children are more prone to heat rash because they are unable to regulate body temperature as well as adults. 

How Are Heat Rashes Diagnosed?

Heat rash can be diagnosed with a patient history and physical examination. Additional testing is usually not needed unless there is a concern about dehydration or kidney damage.

What Is the Treatment for Heat Rashes?

Initial treatment for heat rashes and mild heat-related illness usually includes:

  • Getting out of a hot, humid environment into a cool, dry environment 
  • Cooling measures such as cool baths or clean cloth dipped in cold water and applied to areas with rash or sunburn
  • Fluid intake
  • Rest/stopping physical activity
  • For skin itching: 
Reviewed on 4/12/2022
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