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Heat-related Illnesses and First Aid

Illustration of a man's head who seems to have a high body temperature

Heat stroke, the most serious form of heat-related illness, happens when the body becomes unable to regulate its core temperature. Sweating stops and the body can no longer rid itself of excess heat. Signs include confusion, loss of consciousness, and seizures. "Heat stroke is a medical emergency that may result in death! Call 911 immediately.

Illustration of a man's head who sweating

Heat exhaustion is the body's response to loss of water and salt from heavy sweating. Signs include headache, nausea, dizziness, weakness, irritability, thirst, and heavy sweating.

Illustration of a leg which denotes cramping

Heat cramps are caused by the loss of body salts and fluid during sweating. Low salt levels in muscles cause painful cramps. Tired muscles—those used for performing the work—are usually the ones most affected by cramps. Cramps may occur during or after working hours.

Heat rash, also known as prickly heat, is skin irritation caused by sweat that does not evaporate from the skin. Heat rash is the most common problem in hot work environments.

The chart below shows symptoms and first aid measures to take if a worker shows signs of a heat-related illness.

Illness Symptoms First Aid*
Heat stroke
  • Confusion
  • Fainting
  • Seizures
  • Excessive sweating or red, hot, dry skin
  • Very high body temperature
  • Call 911

While waiting for help:

  • Place worker in shady, cool area
  • Loosen clothing, remove outer clothing
  • Fan air on worker; cold packs in armpits
  • Wet worker with cool water; apply ice packs, cool compresses, or ice if available
  • Provide fluids (preferably water) as soon as possible
  • Stay with worker until help arrives
Heat exhaustion
  • Cool, moist skin
  • Heavy sweating
  • Headache
  • Nausea or vomiting
  • Dizziness
  • Light headedness
  • Weakness
  • Thirst
  • Irritability
  • Fast heart beat
  • Have worker sit or lie down in a cool, shady area
  • Give worker plenty of water or other cool beverages to drink
  • Cool worker with cold compresses/ice packs
  • Take to clinic or emergency room for medical evaluation or treatment if signs or symptoms worsen or do not improve within 60 minutes.
  • Do not return to work that day
Heat cramps
  • Muscle spasms
  • Pain
  • Usually in abdomen, arms, or legs
  • Have worker rest in shady, cool area
  • Worker should drink water or other cool beverages
  • Wait a few hours before allowing worker to return to strenuous work
  • Have worker seek medical attention if cramps don't go away
Heat rash
  • Clusters of red bumps on skin
  • Often appears on neck, upper chest, folds of skin
  • Try to work in a cooler, less humid environment when possible
  • Keep the affected area dry
* Remember, if you are not a medical professional, use this information as a guide only to help workers in need.
For more information about heat-related illnesses:

**These resources were adapted from: California OSHA's heat campaign materials.

***California and Washington state have their own heat illness prevention standards; these materials reflect the requirements in those standards.


*Accessibility Assistance: Contact OSHA's Directorate of Technical Support and Emergency Management at (202) 693-2300 for assistance accessing PDF materials.

All other documents, that are not PDF materials or formatted for the web, are available as Microsoft Office® formats and videos and are noted accordingly. If additional assistance is needed with reading, reviewing or accessing these documents or any figures and illustrations, please also contact OSHA's Directorate of Technical Support and Emergency Management at (202) 693-2300.

**eBooks - EPUB is the most common format for e-Books. If you use a Sony Reader, a Nook, or an iPad you can download the EPUB file format. If you use a Kindle, you can download the MOBI file format.

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