Red blotches on the skin can be caused by a number of factors, but the most common culprit during cold weather months, according to the Physicians' Desktop Reference website, is simply dry air (the condition is so common, in fact, that doctors refer to the condition as "water itch"). Humans constantly lose moisture through their skin by normal evaporative cooling processes, and the dry air found in cold climates and winter weather can accelerate the process. As water evaporates, the absence of excess humidity in the air causes the skin to become depleted of its natural lubrication; when the skin becomes very dry, it may appear as flaky or red with white, scaly areas. The areas most commonly affected are the face, hands, feet, shins and forearms, though any part of the body may lose enough water to appear red and splotchy during cold weather.
While outside air is generally very dry in cold climates, the air quality inside homes and offices may actually contribute to dry skin conditions. Central heat and air systems are designed to reduce humidity as they condition the air, as many areas are either humid year-round or subject to oppressive humidity during the summers. Individuals who work in offices and live in homes with central heat and air are almost constantly exposed to dry conditions during periods of cold weather, so the skin is not afforded opportunities to rehydrate itself. In addition, the cold, dry wind common during cold weather can pick up moisture on the skin's surface and carry it away, causing the skin to maintain a red, irritated appearance. For this reason, individuals who must be frequently outside during winter months should use moisturising lotions and body washes to keep their skin hydrated, and those who live in homes with central heat and air may consider using a humidifier during the winter.
Although cold, dry conditions can make anyone's skin appear red and blotchy, some people with certain medical conditions are simply predisposed to this appearance. When individuals who suffer from rosacea and eczema are exposed to cold, blustery conditions, for example, their pre-existing skin condition becomes agitated and causes the skin to become red and blotchy (this condition is sometimes accompanied by a rash). Other medical conditions like viruses and bacterial infections can also cause red blotchy skin, and these conditions may become more common during cold weather as people spend more time sharing space with others inside heated areas. While skin conditioners, moisturisers and lotions generally help relieve red, blotchy skin during cold weather, those who suspect that their skin problems are caused by more serious medical conditions should consult a doctor for proper treatment.