How can we explain dry lips in winter?

Dry lips in winter: why are they so sensitive during this season?

In winter, the skin is severely tested and undergoes numerous assaults. Although the entire body is affected, the lips are among the most vulnerable areas during this season. Why are they so sensitive? Let's explore together the reasons behind this winter fragility.

Published on January 15, 2025, by Pauline, Chemical Engineer — 6 min of reading

The lips, an inherently delicate area.

If lips are often dry in winter, it is primarily due to their unique structure which makes them highly vulnerable to external aggressions. Indeed, unlike the skin on the rest of the face, the skin on the lips is made up of a very thin epidermis, composed of only three to five layers of cells, compared to about fifteen elsewhere on the body. Furthermore, lips contain only a small amount of ceramides compared to the rest of the body. However, ceramides play a key role in hydration. These lipids occupy the space between each of the cells in the horny layer, which helps to hold the corneocytes together. They thus ensure the skin's barrier function and prevent water from evaporating from the skin cells.

Furthermore, lips lack sebaceous and sweat glands, the organs that respectively produce sebum and sweat. These elements contribute to the composition of the hydrolipidic film, the aqueous/oily mantle that covers the rest of the body and serves a protective function. Indeed, this film acts as a barrier against external factors, such as cold, wind or pollution, and helps to retain water in the stratum corneum. In the absence of this hydrolipidic film, the lips are particularly vulnerable to dehydration and irritations, such as chapping.

Due to their unique structure, dry lips are relatively common and are particularly exacerbated by the harshness of winter.

Cold and dry air, a winter enemy of the lips.

In winter, temperatures drop and the air becomes colder and drier. This phenomenon has a direct impact on the skin and tends to make it dry and irritated. Under normal conditions, the epidermis acts as a semi-permeable barrier, allowing for constant exchanges of water between the inner layers of the skin and the external environment. However, when the air is dry, the water contained in the lips evaporates quickly into the atmosphere. This process is exacerbated by the wind, which accelerates evaporation and leaves the lips dry and prone to chapping.

Furthermore, low temperatures contribute to the drying out of lips by reducing blood flow in the skin tissues, including those of the lips. This decrease in vascularisation, a natural defence mechanism to preserve body heat, reduces the supply of nutrients and oxygen necessary for tissue repair and maintenance. As a result: the lips, already weakened, lose even more of their ability to protect and regenerate themselves against winter assaults and dry out. In some extreme cases, the lips can crack and start to bleed.

The effects of dry air are exacerbated by the global trend of increasing indoor heating, which reduces ambient humidity and impacts skin hydration, particularly that of the lips.

Licking your lips, a particularly harmful reflex in winter.

Moisturising one's lips is a reflex that many adopt when they become dry. This behaviour, often unconscious, can provide temporary relief. However, it is a false friend whose consequences are exacerbated in winter. Indeed, in addition to water, saliva contains digestive enzymes, such as amylase and lipase, which help to break down food but are not suited to the delicate skin of the lips. These enzymes can damage the skin barrier of the lips, which is naturally not very resistant.

Furthermore, in winter, when the air is cold and dry, the evaporation of the moisture deposited by saliva is accelerated. This process amplifies the dehydration of the lips and the onset of dry lips, as the evaporating water carries away some of the skin's water reserves. A vicious cycle then sets in, where the lips become increasingly dry, prompting the habit of licking, even though it contributes to water loss.