During the winter months, I hear a lot of concern from patients about frostbite. Frostbite is a very real danger in extremely cold weather. However, patients often confuse other dermatological conditions – such as frostnip, Raynaud’s phenomenon, and pernio – with frostbite. I hope to clear up some of the confusion by explaining these conditions here.
True frostbite is the direct freezing of tissue due to cold exposure. Classic frostbite scenarios include hikers lost in the woods in cold weather and mountain climbers who become trapped. Virtually any situation where people are unable to get out of the elements puts them at risk for having their tissue actually freeze due to the extremes of weather.
Like frostbite, frostnip develops from cold exposure, but it is much less severe than frostbite. Frostnip is indicated by pale, numb, and tingling skin without necessarily direct freezing. Children who spend long periods of time playing outdoors in the winter or skiers at the end of the day can find that they’ve developed frostnip on the fingers and toes. Gentle rewarming with warm (not hot!) water is helpful in recovery.
There are two other skin conditions which people mistakenly call frostbite. This is because both conditions are usually triggered by cold temperatures. These are specific conditions and not symptoms of actual frozen tissue.
The first is Raynaud’s phenomenon. Raynaud’s phenomenon typically occurs in the fingers and toes and is triggered by cold temperatures. Cold weather during winter is one of the main causes, but this condition can also develop in hot summer months from holding an icy cold beverage. Raynaud’s phenomenon is caused by spasm of the blood vessels in response to the cold. Fingers will turn white, then a bluish color, and finally red.
The white color occurs when blood vessels clamp down and decrease blood flow to the fingers and/or toes. The extremity then appears bluish from the resulting lack of blood flow. This stage is called cyanosis. Finally, as the vessels relax, blood rushes back into the extremities resulting in reddish color to the skin.
Raynaud’s phenomenon can develop on its own for no known reason or it can be associated with other diseases, usually autoimmune diseases such as lupus, scleroderma, dermatomyositis, and rheumatoid arthritis.
The second skin condition often mistakenly called frostbite is pernio, also known as chilblains. Similar to Raynaud’s phenomenon, pernio is also an abnormal vascular response that usually happens in the cold weather. People who are susceptible to pernio will develop the condition after being outside for long periods of time – shoveling snow, skiing, or playing for example. People with pernio develop painful lesions and itchy bumps on the fingers or toes. Pernio, or chilblains, can develop with a day of cold exposure and last for several weeks.
There are usually no internal problems associated with pernio, although some diseases can be associated with it (such as some forms of leukemia and lupus). Sometimes pernio lesions require a certain amount of humidity to develop. In this case, the lesions are more common on the feet where the humidity is high in shoes or boots. Generally, the condition is self-resolving and does not require treatment; however, there are some oral medications to increase blood flow that may be prescribed by a doctor.
While Raynaud’s phenomenon and pernio are not frostbite, they are painful. As a preventative measure in cold weather, your goal is to keep your hands and feet warm and dry. If your extremities are cold, rewarming with skin-to-skin contact is effective: putting your hands under your arms or holding your fingers in a fist to provide warmth. You can also gently rub the skin, taking great care not to rub vigorously.