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What is heat illness?

Heat illness includes several disorders that can occur when body temperature increases

The most common types of heat illness are heat cramps, heat rash, heat exhaustion, and the most severe, heat stroke. The content below provides a brief overview of body temperature regulation and a description (including symptoms and treatment) of the heat illnesses previously mentioned.

How is body temperature regulated?

Normal body temperature is typically between 97.80 - 98.60 degrees Fahrenheit.  It is regulated by a small region in the brain called the preoptic anterior hypothalamus.   Receptors located internally monitor core body temperature while skin receptors sense surface temperature and our environment.  These receptors send information to the brain, and if body temperature begins to rise we enact mechanisms to help remove heat.  This includes redirecting warm blood to the surface of the skin to help with heat transfer to the environment along with sweating.  Importantly, for sweating to be effective for cooling it must evaporate from your skin.  For this reason, cooling from sweat is more efficient in dry climates.  Conversely, high humidity presents a major challenge for cooling because sweat doesn't evaporate very well.  Check out my blog on "Why humid environments are dangerous?".

Sweating (and evaporation) do a great job to prevent a rise in body temperature.  However, if one remains in a hot environment a high sweat rate must be maintained through proper hydration strategies.  For example, evidence shows that humans can sweat upwards of 0.5 - 2 liters/hour depending on what you're doing (i.e., exercising or working) and environmental conditions.  Another strategy to combat the increase in body temperature is taking consistent rest breaks from the heat.  If fluids are not replaced and someone does not properly rest then body temperature will increase.  An increase in body temperature by as much as 3-4 degrees Farenheit can often be managed, but the risk for heat illness increases as temperature continues to rise. 

Heat Rash

Heat rash is a reddish colored skin irritation that present as small pimples or even blisters on the neck, upper chest (under breasts), groin creases, and in the elbow crease.  It occurs in response to excessive sweating and skin moisture.

How to treat?

    • Try to move or work in cooler and dryer area
      • Keep area dry (powders can be used to help)
        • Ointments and moisturizers are not recommended

          Heat Cramps

          Heat cramps typically occur earlier than more severe conditions, but can also be a sign of heat exhaustion (see below).  Symptoms include excessive muscle cramping and spasms in the arms and legs.  The cause is complex and may be due to water and electrolyte losses that occur from heavy sweating.  The composition of sweat includes water and electrolytes (potassium and sodium), which play important roles in muscle contraction, and depletion is linked to muscle cramping.

          How to treat?

              • Rest and removal from hot environment
              • Drink fluids, including a carbohydrate drink that contains electrolytes every 15-20 minutes.
              • Eating food will also help to restore electrolytes
              • Avoid large sodium intake such as salt tablets or drinks with excessive sodium levels (above 500 mg).

                Heat Exhaustion

                Heat exhaustion is a serious condition, that can be sometimes hard to identify because it includes similar symptoms of other heat related illnesses.  It happens as body temperature rises as a result of prolonged exposure and sweating.  Symptoms often include feelings of weakness, thirst, heavy sweating, nausea, and clammy skin (see figure below).

                How to treat?

                  • Remove from heat and place in cooler environment (e.g., air conditioning or shade with fans)
                    • Drink fluids, preferably cold water
                      • Remove unnecessary clothing
                        • If available, use cooling strategies such as cold towels, ice packs, splash cool water on face and body
                          • If symptoms don't improve, then call 911

                            Heat stroke

                            Recognizing symptoms of heat exhaustion will prevent the escalation to heat stroke, which is a life threatening condition.  Heat stroke is a situation where your body can no longer regulate temperature and it can increase rapidly in a matter of minutes.  It often happens when core temperature increases above 104 degrees Fahrenheit.  Symptoms include dizziness, confusion, headache, lack of sweating, and loss of consciousness.

                            How to treat?

                              • Call 911
                                • Remove outer clothing and remove from hot environment
                                  • Cool the person immediately by placing them cool water up to their neck if available
                                    • Use other cooling strategies such as cover their body with ice, cold towels, circulate cool air
                                      • Place ice packs/cold towels around neck, armpits, and groin region.

                                         Symptoms of heat exhaustion versus heat stroke

                                         Conclusion

                                        Heat illness includes several heat-related disorders that can be severe.   They can occur during prolonged exposure to a hot environment that causes excessive sweating.  It is important to recognize symptoms early on to prevent more dangerous conditions such as heat exhaustion and stroke.  The National Institute for Occupational Safety and Health is great resource for learning about heat illnesses, treatment, and prevention strategies.

                                        By Micah Zuhl, Ph.D.

                                         

                                         

                                         

                                         

                                         

                                         

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