How does the skin regulate body temperature when a patient has either hyperthermia or hypothermia?

Low body temperature; Cold exposure; Exposure

Hypothermia is dangerously low body temperature, below 95°F (35°C).

The skin is the largest organ of the body. The skin and its derivatives (hair, nails, sweat and oil glands) make up the integumentary system. One of the main functions of the skin is protection. It protects the body from external factors such as bacteria, chemicals, and temperature. The skin contains secretions that can kill bacteria and the pigment melanin provides a chemical pigment defense against ultraviolet light that can damage skin cells. Another important function of the skin is body temperature regulation. When the skin is exposed to a cold temperature, the blood vessels in the dermis constrict. This allows the blood which is warm, to bypass the skin. The skin then becomes the temperature of the cold it is exposed to. Body heat is conserved since the blood vessels are not diverting heat to the skin anymore. Among its many functions the skin is an incredible organ always protecting the body from external agents.

Other types of cold injuries that affect the limbs are called peripheral cold injuries. Of these, frostbite is the most common freezing injury. Nonfreezing injuries that occur from exposure to cold wet conditions include trench foot and immersion foot conditions. Chilblains (also known as pernio) are small, itchy or painful lumps on the skin that often occur on the fingers, ears, or toes. They are a type of nonfreezing injury that develops in cold, dry conditions.

You are more likely to develop hypothermia if you are:

Very old or very young
Chronically ill, especially people who have heart or blood flow problems
Malnourished
Overly tired
Taking certain prescription medicines
Under the influence of alcohol or drugs

Hypothermia occurs when more heat is lost than the body can make. In most cases, it occurs after long periods in the cold.

Common causes include:

Being outside without enough protective clothing in winter
Falling into cold water of a lake, river, or other body of water
Wearing wet clothing in windy or cold weather
Heavy exertion, not drinking enough fluids, or not eating enough in cold weather

As a person develops hypothermia, they slowly lose the ability to think and move. In fact, they may even be unaware that they need emergency treatment. Someone with hypothermia also is likely to have frostbite.

The symptoms include:

Confusion
Drowsiness
Pale and cold skin
Slowed breathing or heart rate
Shivering that cannot be controlled (although at extremely low body temperatures, shivering may stop)
Weakness and loss of coordination

Lethargy (weakness and sleepiness), cardiac arrest, shock, and coma can set in without prompt treatment. Hypothermia can be fatal.

Take the following steps if you think someone has hypothermia:

If the person has any symptoms of hypothermia that are present, especially confusion or problems thinking, call 911 right away.
If the person is unconscious, check airway, breathing, and circulation. If necessary, begin rescue breathing or CPR. If the victim is breathing fewer than 6 breaths per minute, begin rescue breathing.
Take the person inside to room temperature and cover with warm blankets. If going indoors is not possible, get the person out of the wind and use a blanket to provide insulation from the cold ground. Cover the person's head and neck to help retain body heat.
Victims of severe hypothermia should be removed from the cold environment with as little exertion as possible. This helps to avoid warmth from being shunted from the person's core to the muscles. In a very mildly hypothermic person, muscular exercise is thought to be safe, however.
Once inside, remove any wet or tight clothes and replace them with dry clothing.
Warm the person. If necessary, use your own body heat to aid the warming. Apply warm compresses to the neck, chest wall, and groin. If the person is alert and can easily swallow, give warm, sweetened, nonalcoholic fluids to aid the warming.
Stay with the person until medical help arrives.

Follow these precautions:

DO NOT assume that someone found lying motionless in the cold is already dead.
DO NOT use direct heat (such as hot water, a heating pad, or a heat lamp) to warm the person.
DO NOT give the person alcohol.

Call 911 or the local emergency number anytime you suspect someone has hypothermia. Give first aid while waiting for emergency help.

Before you spend time outside in the cold, DO NOT drink alcohol or smoke. Drink plenty of fluids and get enough food and rest.

Wear proper clothing in cold temperatures to protect your body. These include:

Mittens (not gloves)
Wind-proof, water-resistant, many-layered clothing
Two pairs of socks (avoid cotton)
Scarf and hat that cover the ears (to avoid major heat loss through the top of your head)

Avoid:

Extremely cold temperatures, especially with high winds
Wet clothes
Poor circulation, which is more likely from age, tight clothing or boots, cramped positions, fatigue, certain medicines, smoking, and alcohol

Prendergast HM, Erickson TB. Procedures pertaining to hypothermia and hyperthermia. In: Roberts JR, Custalow CB, Thomsen TW, eds. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 65.

Zafren K, Danzl DF. Frostbite and nonfreezing cold injuries. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier; 2018:chap 131.

Zafren K, Danzl DF. Accidental hypothermia. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier; 2018:chap 132.

Sawka MN, O'Connor FG. Disorders due to heat and cold. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 101.

Last reviewed on: 11/13/2021

Reviewed by: Jesse Borke, MD, CPE, FAAEM, FACEP, Attending Physician at Kaiser Permanente, Orange County, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

Learning Outcomes

Explain how the skin helps maintain body temperature

Body temperature is primarily regulated by an area in the brain known as the hypothalamus. The hypothalamus sets the body’s temperature and controls it by opening and closing sweat glands and contracting muscles.

The integumentary system helps regulate body temperature through its tight association with the sympathetic nervous system, the division of the nervous system involved in our fight-or-flight responses. The sympathetic nervous system is continuously monitoring body temperature and initiating appropriate motor responses.

Recall that sudoriferous glands, accessory structures to the skin, secrete sweat to cool the body when it becomes warm. Even when the body does not appear to be noticeably sweating, approximately 500 mL of sweat (insensible perspiration) are secreted a day. If the body becomes excessively warm due to high temperatures, vigorous activity (Figure 1), or a combination of the two, sweat glands will be stimulated by the sympathetic nervous system to produce large amounts of sweat, as much as 0.7 to 1.5 L per hour for an active person. When the sweat evaporates from the skin surface, the body is cooled as body heat is dissipated.

In addition to sweating, arterioles in the dermis dilate so that excess heat carried by the blood can dissipate through the skin and into the surrounding environment (Figure 1). This accounts for the skin redness that many people experience when exercising.

Figure 1. During strenuous physical activities, such as skiing (a) or running (c), the dermal blood vessels dilate and sweat secretion increases (b). These mechanisms prevent the body from overheating. In contrast, the dermal blood vessels constrict to minimize heat loss in response to low temperatures (b). (credit a: “Trysil”/flickr; credit c: Ralph Daily)

When body temperatures drop, the arterioles constrict to minimize heat loss, particularly in the ends of the digits and tip of the nose. This reduced circulation can result in the skin taking on a whitish hue. Although the temperature of the skin drops as a result, passive heat loss is prevented, and internal organs and structures remain warm. If the temperature of the skin drops too much (such as environmental temperatures below freezing), the conservation of body core heat can result in the skin actually freezing, a condition called frostbite.

Why do people sweat excessively when exercising outside on a hot day?

Explain your skin’s response to a drop in body core temperature.