Emergency room doctors are urging people to protect themselves from winter’s deadly companions, hypothermia and frostbite.

Be alert, says the American College of Emergency Physicians (ACEP), for the warning signs of hypothermia such as constant shivering and pale, dry skin, and of frostbite, when skin patches may turn pale and become numb - and seek help if these symptoms develop.

Hypothermia occurs when body temperature falls below normal, while frostbite happens when the skin freezes.

Frostbite can result from low air temperatures, wet clothes or forceful winds. Body parts that are normally first to fall to frostbite include the fingers, toes, earlobes, cheeks and other regions that are most exposed to cold.

There are steps people can take and situations they should avoid to prevent frostbite and hypothermia, the ACEP advises.

Wear multiple layers, which trap warm air between them. Hats are also very important, since a lot of heat is lost from the head.

Tobacco can constrict circulation, which limits the blood’s ability to circulate heat around the body, Dr. Doug Hill, spokesperson for the ACEP, told Reuters Health. Chewing and smoking tobacco don’t cause frostbite or hypothermia, he said, but rather aggravate the problem once it occurs.

Stay dry, since water removes heat from the body and can cause problems in “minutes,” Hill said.

Many medications can affect circulation; ask your doctor if what you are taking could increase your risks from the cold, Hill recommended.

Limit alcohol when in a cold environment, since it can stop shivering - the body’s tool to generate warmth - and open up blood vessels, causing loss of body heat from the extremities, Hill noted.

Staying active in cold temperatures helps by increasing metabolism, he said, which in turn raises body heat.

Apart from shivering and a pallid skin, other symptoms of hypothermia include confusion, sleepiness, irrational behavior, slurred speech, memory loss, and slow or shallow breathing.

The feeling of “pins and needles” in the skin is an additional warning sign of frostbite, according to the ACEP.

If you feel these symptoms in cold weather or notice them in a companion, get to a warm place as soon as possible, Hill recommended. “The best thing to do is to terminate exposure - get out of it,” he said in an interview.

As soon as a person begins shivering, they are, by definition, in a state of hypothermia, Hill explained. Severe repercussions typically occur after “hours” of shivering, but they can happen much more quickly if people are also wet, he noted.

The bottom line: the best way to protect yourself from hypothermia and frostbite is to prevent either from ever occurring, he added. “The best treatment of anything, is prevention,” Hill said.