Things you need to know:

• Heat illness can strike quickly. Stop working, get cool, and drink fluids.

• When treating severe heat illness, cooling is the first priority.

• Altered mental state can be a sign of heat stroke and requires 

immediate attention.

• Muscle cramps, pain, or spasms in the abdomen, arms, or legs—

alone or with any symptom—should not be ignored.

• Never leave a worker with heat illness alone. 

heat stress

First Aid for 

Heat Illness

Cooling is key. Know the symptoms 

and treatment of heat illness.*

Symptoms can occur in any order. You don't need to have all of the symptoms in a category to have heat illness.

Signs and Symptoms What to Do

Heat Rash/ 

Prickly Heat

• Red cluster of pimples or small blisters, 

usually on neck, upper chest, groin, 

under breasts, and in elbow creases

• Extensive areas of skin that do not 

sweat on heat exposure, but present a 

gooseflesh appearance that subsides 

with cool environments

• When possible, a cooler, less humid work environment 

is the best treatment

• Keep rash area dry

• Do not use ointments or creams, as they may impair 

cooling—warm, moist skin can make the rash worse

Heat 

Cramps

• Muscle cramps, pain, or spasms in the 

abdomen, arms, or legs

• Drink fluids every 15 to 20 minutes and eat a snack or 

sports drink

• Avoid salt tablets, but drinks containing electrolytes are OK

• Get medical help if the worker has heart problems, is on a 

low sodium diet, or if cramps do not subside within 1 hour

Heat 

Syncope 

(Fainting)

 

• Fainting, dizziness, or lightheadedness after standing or suddenly 

rising from a sitting/lying position

• Sit or lie down in a cool place when beginning to feel 

faint or dizzy

• Slowly drink water or clear juice

Heat 

Exhaustion

• Headache

• Nausea

• Dizziness, weakness

• Irritability

• Thirst, heavy sweating

• Elevated body temperature

• Decreased urine output

 

• Call for medical help or take worker to a health facility for 

evaluation and treatment

• Stay with worker until help arrives 

• Remove worker from hot area and give liquids to drink

• Remove unnecessary clothing, including shoes and socks

• Cool worker with water, cold compresses, an ice bath, or fans

• Encourage frequent sips of cool water

Exertional 

Heat Stroke

• Confusion, altered mental 

state, slurred speech, loss of 

consciousness

• Hot, dry skin or profuse sweating

• Seizures

• Very high body temperatures

• Fatal if treatment delayed

• This is an emergency! Call for emergency care immediately!

• Move worker to a cool area and remove clothing

• Immerse worker in a tub of ice water

• If a tub is not available, place worker in a tarp with ice and 

water (e.g., tarp-assisted cooling with oscillation†

) 

• If cold-water immersion is not possible,

• Soak worker with cold water from a hose or shower

• Apply cold, wet towels to as much of the skin as possible, 

and replace towels frequently

Centers for Disease Control

and Prevention

National Institute for Occupational 

Safety and Health
heat stress First Aid

Header photos by ©mycola/iStock

Case Study: Heat Stroke

A 44-year-old male worker died of heat stroke while 

working on a North Carolina farm. The man had been 

working in the fields for about a week. On August 1st, the 

heat index was between 100°F and 110°F. The heat index 

reports how hot it feels to people outside based on the air 

temperature and humidity.

Around 3 p.m., the worker complained to the crew 

leader that he was feeling ill. He drank some water and 

was driven to the employee housing and left alone. He 

was found unconscious 45 minutes later. Emergency 

personnel took the worker to the hospital, where he was 

pronounced dead. His core body temperature was 108°F.

Lessons Learned

• Feeling ill while working in the heat is a serious warning sign. Any employee who reports feeling 

unwell during work in hot conditions could have heat exhaustion, which can quickly progress to heat 

stroke if not treated.

• Proper first aid for someone with suspected heat exhaustion or heat stroke involves COOLING 

the body as quickly as possible—not simply drinking water.

• People with severe heat illness do not always recognize the risks they face. If a worker shows 

signs of heat exhaustion or heat stroke, do not leave him or her alone until he or she receives 

medical attention.

Photo by ©Thinkstock

*

For more information about heat exposure at work, see NIOSH [2016]. Criteria for a recommended standard: occupational exposure to heat 

and hot environments. By Jacklitsch B, Williams J, Musolin K, Coca A, Kim J, Turner N. Cincinnati, OH: U.S. Department of Health and Human 

Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 

2016-106, https://www.cdc.gov/niosh/docs/2016-106/.

†

For more information on tarp-assisted cooling with oscillation, see Luhring KE, Butts CL, Smith CR, Bonacci JA, Ylanan RC, Ganio MS, 

McDermott BP [2016]. Cooling effectiveness of a modified cold-water immersion method after exercise-induced hyperthermia. J Athl Train 

51(11):946–951

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DHHS (NIOSH) Publication No. 2024-100

DOI: https://doi.org/10.26616/NIOSHPUB2024100

October 2023