Rosacea: How can we explain the redness that marks the face?

Redness on the face, also referred to as facial erythema when temporary or erythrosis when it becomes permanent, represents the initial stage of rosacea. Particularly noticeable on fair skin, this redness is the result of the dilation of small, fine, red or purplish blood vessels on the skin's surface, which become visible to the naked eye (telangiectasias). Moreover, individuals suffering from rosacea have highly sensitive skin and a compromised skin barrier. This characteristic contributes to the visibility of these blood vessels. Several factors can explain the increase in the diameter of the capillaries.

• Heat : an increase in temperature is the primary cause of redness. Indeed, when the TRVP1 receptors in the epidermis are subjected to a thermal stimulus, they respond by triggering a nociceptive mechanism that leads to the dilation of blood vessels and consequently to the onset of redness.

• Certain foods : similar to heat, capsaicin, a molecule found in chili peppers, bell peppers, and black pepper, can stimulate the activity of the TRVP1 receptor, thereby causing the dilation of blood vessels.

• Stress : Stress is also a trigger factor for redness in the case of rosacea. Indeed, significant stress leads to the release of certain neuropeptides, such as PACAP and CGRP. These act on the blood vessels causing vasodilation, which is the origin of the blushing and persistent erythema found in rosacea.

• The UVB rays of the sun : UVB rays interact with the TRVP4 receptors in the epidermis, which are partly responsible for the deterioration of skin tissues due to sun exposure. The stimulation of these receptors triggers nociceptive mechanisms, alters the structure of the skin, and leads to the onset of redness.

• A Parasitic Colonization : A high density of Demodex, parasites that inhabit the hair and sebaceous regions of the skin, can also cause redness. If we delve into the biology at work, the Demodex secrete proteases that increase the activity of PAR-2 receptors (protease-activated receptor) present in the epidermis. This activation subsequently triggers the release of TNF-α and interleukin-1 (IL-1), inflammatory agents responsible for the redness and inflammation observed in individuals suffering from rosacea.

• Heredity : Scientists also suspect that certain yet-to-be-identified genes are involved in the pathogenesis of rosacea and the redness it causes. One considered hypothesis is the prevalence among individuals suffering from rosacea of certain receptors involved in inflammatory mechanisms. This prevalence could be due to a high expression of the genes coding for these receptors.

As of today, there is no definitive treatment for rosacea. However, if you suffer from redness due to your rosacea, your dermatologist may prescribe creams or gels for topical application. These creams are formulated with active ingredients that have vasoconstrictive properties such as brimonidine, anti-inflammatory properties, like ivermectin, and antiparasitic properties, like metronidazole. It's worth noting that these can be used both preventively and curatively. Laser and intense pulsed light treatments can also help reduce redness and the visibility of blood vessels by decreasing their dilation.

Some natural alternatives also help to reduce the redness caused by rosacea. Indeed, aloe vera, green tea extract, and chamomile have anti-inflammatory and antioxidant properties that are beneficial in cases of dermatosis, and their effectiveness in reducing redness has been demonstrated in several studies. Finally, daily routines such as applying a moisturizing cream and a sun care product can also help to soothe the skin and prevent and reduce redness.