When it's cold outside, blood flow through the capillaries almost ceases. The skin's entire blood supply is reduced because blood needs to return to the inside of the body as quickly as possible. Otherwise, there's a risk that the surface will lose too much heat, and the temperature will drop even further.
From this, we can conclude that in the cold, the skin receives less oxygen. For a while, it can cope with this without problems. But in severe cold, the body's extremities—such as the nose, fingers, toes, and ears—are at risk.
You might immediately think that sub-zero temperatures are needed to harm the skin. In fact, frostbite can occur even at moderate temperatures, for example, at +4°C. This temperature, which is common in refrigerators, is enough to significantly reduce blood flow to the skin. The skin then becomes inflamed and swollen.
In general, skin adapts well to the cold. In winter, it's a bit drier because the air in heated rooms and the dry air outside lead to greater moisture loss. But you shouldn't immediately grab a jar of cream. Unless, of course, you feel that your skin can't cope on its own. Moisturizers should only be applied in the evening before bed, and only if you are prone to excessive skin dryness.
If you apply a moisturizer before going out into the bitter cold, you can easily get frostbite. The culprit is the high water content in the products.
The dryness of the skin in the cold season has another significant cause. We have two sources of skin oil:
—Barrier lipids of the stratum corneum;
—Sebum from the sebaceous glands.
The latter are found in large numbers on the head, ears, and face, especially in the so-called T-zone: the forehead, nose, and chin. Poor lips, on the other hand, have no sebaceous glands at all, so they constantly need oil from an external source.
Sebum behaves much like butter. When it's warm, it forms droplets. Just as butter becomes easy to spread at room temperature, these droplets are distributed across the face like butter on a sandwich. But when the temperature is like it is in a refrigerator, the sebum becomes solid. In winter, it is less effectively distributed, the skin becomes drier, and the lips, in particular, are neglected, becoming dry and chapped. If you also constantly lick them with your tongue, then all is lost. Because that means even less oil and even more water, which increases the risk of frostbite.
The idea that the sebaceous glands stop working in the cold is just a common myth, as they are located deep in the dermis, so all processes there continue unimpeded. This is confirmed by the fact that acne does not heal in winter, nor does oily eczema, which results from excessive sebum secretion.
On the contrary, these ailments worsen, as the anti-inflammatory effect of sunlight disappears. The sun and its ultraviolet radiation can, in many cases, reduce inflammatory processes on the skin, similar to cortisone cream. This effect is felt at the Dead Sea or in medical UV radiation rooms, where conditions like neurodermatitis and psoriasis are treated.
