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How Heat and Sun Affects the Body Human
Human bodies dissipate heat by varying the rate and depth of blood circulation, by losing water through the skin and sweat glands, and-as the last extremity is reached-by panting, when blood is heated above 98.6 degrees. The heart begins to pump more blood, blood vessels dilate to accommodate the increased flow, and the bundles of tiny capillaries threading through the upper layers of skin are put into operation. The body’s blood is circulated closer to the skin’s surface, and excess heat drains off into the cooler atmosphere. At the same time, water diffuses through the skin as perspiration. The skin handles about 90 percent of the body’s heat dissipating function.
Sweating, by itself, does nothing to cool the body, unless the water is removed by evaporation, and high relative humidity retards evaporation. The evaporation process itself works this way: the heat energy required to evaporate the sweat is extracted from the body, thereby cooling it. Under conditions of high temperature (above 90 degrees) and high relative humidity, the body is doing everything it can to maintain 98.6 degrees inside. The heart is pumping a torrent of blood through dilated circulatory vessels; the sweat glands are pouring liquid-including essential dissolved chemicals, like sodium and chloride onto the surface of the skin.
Sunburn, with its ultraviolet radiation burns, can significantly retard the skin’s ability to shed excess heat. Studies indicate that, other things being equal, the severity of heat disorders tend to increase with age-heat cramps in a 17-year-old may be heat exhaustion in someone 40, and heat stroke in a person over 60.
Preventing Heat-Related Illness
Elderly persons, small children, chronic invalids, those on certain medications or drugs (especially tranquilizers and anticholinergics), and persons with weight and alcohol problems are particularly susceptible to heat reactions, especially during heat waves in areas where a moderate climate usually prevails.
Heat Wave Safety Tips
- Slow down. Strenuous activities should be reduced, eliminated, or rescheduled to the coolest time of the day. Individuals at risk should stay in the coolest available place, not necessarily indoors.
- Dress for summer. Lightweight light-colored clothing reflects heat and sunlight, and helps your body maintain normal temperatures.
- Put less fuel on your inner fires. Foods (like proteins) that increase metabolic heat production also increase water loss.
- Drink plenty of water or other non-alcohol fluids. Your body needs water to keep cool. Drink plenty of fluids even if you don’t feel thirsty. Persons who (1) have epilepsy or heart, kidney, or liver disease, (2) are on fluid restrictive diets or (3) have a problem with fluid retention should consult a physician before increasing their consumption of fluids.
- Do not drink alcoholic beverages.
- Do not take salt tablets unless specified by a physician.
- Spend more time in air-conditioned places. Air conditioning in homes and other buildings markedly reduces danger from the heat. If you cannot afford an air conditioner, spending some time each day (during hot weather) in an air conditioned environment affords some protection.
- Don’t get too much sun. Sunburn makes the job of heat dissipation that much more difficult.
Know These Heat Disorder Symptoms
SUNBURN: Redness and pain. In severe cases swelling of skin, blisters, fever, headaches. First Aid: Ointments for mild cases if blisters appear and do not break. If breaking occurs, apply dry sterile dressing. Serious, extensive cases should be seen by physician.
HEAT CRAMPS: Painful spasms usually in muscles of legs and abdomen possible. Heavy sweating. First Aid: Firm pressure on cramping muscles, or gentle massage to relieve spasm. Give sips of water. If nausea occurs, discontinue use.
HEAT EXHAUSTION: Heavy sweating, weakness, skin cold, pale and clammy. Pulse thready. Normal temperature possible. Fainting and vomiting. First Aid: Get victim out of sun. Lay down and loosen clothing. Apply cool, wet cloths. Fan or move victim to air conditioned room. Sips of water. If nausea occurs, discontinue use. If vomiting continues, seek immediate medical attention.
HEAT STROKE (or sunstroke): High body temperature (106° F. or higher). Hot dry skin. Rapid and strong pulse. Possible unconsciousness. First Aid: HEAT STROKE IS A SEVERE MEDICAL EMERGENCY. SUMMON EMERGENCY MEDICAL ASSISTANCE OR GET THE VICTIM TO A HOSPITAL IMMEDIATELY. DELAY CAN BE FATAL. Move the victim to a cooler environment Reduce body temperature with cold bath or sponging. Use extreme caution. Remove clothing, use fans and air conditioners. If temperature rises again, repeat process. Do not give fluids. Persons on salt restrictive diets should consult a physician before increasing their salt intake.
Information from the NOAA’s National Weather Service.
Protect Yourself from Sun Exposure
Anyone outdoors is exposed to the sun’s ultraviolet (UV) rays, even on cloudy days. UV rays are a part of sunlight that is an invisible form of radiation. There are three types of UV rays. UVA is believed to damage connective tissue and increase the risk for developing skin cancer. UVB penetrates less deeply into the skin, but can still cause some types of skin cancer. Natural UVC is absorbed by the atmosphere and does not pose a risk.
Sunburn is not immediately apparent. Symptoms usually start about 4 hours after sun exposure, worsen in 24–36 hours, and resolve in 3–5 days. They include red, tender and swollen skin, blistering, headache, fever, nausea, and fatigue. In addition to the skin, eyes can become sunburned. Sunburned eyes become red, dry, painful, and feel gritty. Chronic eye exposure can cause permanent damage, including blindness.
- Take aspirin, acetaminophen, or ibuprofen to relieve pain, headache, and fever.
- Drink plenty of water to help replace fluid losses.
- Comfort burns with cool baths or the gentle application of cool wet cloths.
- Avoid further exposure until the burn has resolved.
- Use of a topical moisturizing cream, aloe, or 1% hydrocortisone cream may provide additional relief.
If blistering occurs:
- Lightly bandage or cover the area with gauze to prevent infect
- Do not break blisters. (This slows healing and increases risk of infection.)
- When the blisters break and the skin peels, dried skin fragments may be removed and an antiseptic ointment or hydrocortisone cream may be applied.
Seek medical attention if any of the following occur:
• Severe sunburns covering more than 15% of the body
• High fever (>101 °F)
• Extreme pain that persists for longer than 48 hours
- Avoid prolonged exposure to the sun when possible.
- Wear sunscreen with a minimum of SPF 15. SPF refers to how long a person will be protected from a burn. (SPF 15 means a person can stay in the sun 15-times longer before burning.) SPF only refers to UVB protection.
- To protect against UVA, look for products containing: Mexoryl, Parsol 1789, titanium dioxide, zinc oxide, or avobenzone.
- Sunscreen performance is affected by wind, humidity, perspiration, and proper application.
- Throw away sunscreens after 1–2 years (they lose potency).
- Apply liberally (minimum of 1 oz) at least 20 minutes before sun exposure.
- Apply to ears, scalp, lips, neck, tops of feet, and backs of hands.
- Reapply at least every 2 hours and each time a person gets out of the water or perspires heavily.
- Some sunscreens may lose their effectiveness when applied with insect repellents. You may need to reapply more often.
- Wear clothing with a tight weave or high-SPF clothing.
- Wear wide-brimmed hats and sunglasses with UV protection and side panels.
- Take breaks in shaded areas.
This information is from The Centers for Disease Control and Prevention. CDC.gov.