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Heat Stress: Warning Signs

Even severe heat stress can appear suddenly, so it's important to learn the warning signs and how to treat them.

Mild: heat stress

Core body temperature stays at 98.6°F (37°C) (or your normal temperature). It isn't dangerous unless the symptoms aren't treated. Signs and symptoms include:

  • Sweating a lot

  • Having painful spasms in your muscles during activity or hours afterward (heat cramps)

  • Developing tiny red bumps on skin and a prickling sensation (prickly heat)

  • Feeling irritable or weak

Treatment. Get medical advice and do the following:

  • Rest in a cool, shady area.

  • Drink water or a sport drink.

Moderate: heat exhaustion

Core body temperature may rise up to 101°F (38.3°C). It should be treated right away. Signs and symptoms include:

  • Sweating a lot

  • Cold, moist, pale or flushed skin

  • Feeling very weak or tired

  • Headache, nausea, loss of appetite

  • Feeling dizzy or giddy

  • Rapid or weak pulse

  • Fainting or near collapse

  • Persistent muscle cramps

Treatment. Get medical treatment urgently! You may be told to:

  • Rest in a cool, shady area. Lie down with feet above the level of your heart.

  • Remove excess gear and clothing.

  • Drink water or a sport drink. In some cases, a medical professional must administer fluids.

  • Take salt (in some cases).

  • Use cool compresses on the forehead, around the neck, and under armpits.

  • Blow air onto your skin with fans.

  • Go to the emergency department if symptoms don't resolve rapidly. Athletes should recover in about 20 minutes from this type of heat injury.

Severe: heat stroke

This is a serious, life-threatening medical emergency. Core body temperature can rise to 105°F (40.5°C) or more. If not treated right away, heat stroke can lead to permanent brain damage and even death. Signs and symptoms include:

  • Collapse during activity

  • Altered mental state, irrational behavior or not acting like oneself

  • Decreased blood pressure

  • Hot, dry skin that looks red, mottled, or bluish (no sweating)

  • Deep, fast breathing

  • Headache or nausea or vomiting

  • Rapid, weak, or irregular pulse

  • Feeling dizzy, confused, or delirious

  • Fainting

  • Convulsions/seizures

Treatment. Someone should call for emergency help right away. Rapid cooling is extremely important. All efforts should be made to start cooling the person down immediately before help arrives. While waiting for emergency help, the affected person should:

  • Rest in a cool, shady area.

  • Have clothing soaked with cool water. Or, remove outer clothing and be wrapped with a sheet soaked in cool water. Place the person in water in a tub or children's swimming pool if available. Use ice packs and ice water if feasible.

  • Be blown with fans.

  • Drink water or a sport drink. (Don't try to give a drink to someone who is unconscious, seizing, or delirious.)

Online Medical Reviewer: Eric Perez MD
Online Medical Reviewer: Ronald Karlin MD
Online Medical Reviewer: Tara Novick
Date Last Reviewed: 12/1/2021
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