What are the causes of rosacea?

The causes of rosacea are still poorly understood today, and multiple biological mechanisms are thought to be involved in the irritations and hot flushes experienced by patients. Recent studies have revealed that certain factors seem to promote the dilation of blood vessels, a key element of rosacea. Indeed, when the diameter of the capillaries increases, the temperature of the epidermis also tends to rise, which causes redness and sensations of heat. Let's discover together what these factors are that encourage rosacea flare-ups.

Cause No. 1: Genetics.

Up to 30% of individuals suffering from rosacea have a family history of this condition, leading researchers to believe that unidentified genes could be responsible and that, in some cases, it could be a hereditary disorder. One hypothesis being considered is the prevalence among individuals with rosacea of certain receptors involved in inflammatory mechanisms.

Furthermore, it appears that individuals with a lighter phototype are more likely to develop this skin disorder. Statistics also show that women are twice as likely to be affected by rosacea as men, although the reason for this phenomenon is not yet explained.

Cause No. 2: Parasitic Colonisation.

The Demodex, parasites predominantly found in the pilosebaceous regions of the skin, could also promote rosacea flare-ups. Naturally present in the epidermis, they play a seboregulatory role. However, when more than 5 parasites per cm² of skin are observed, it is considered that there is a colonisation by the Demodex.

These secrete proteases, enzymes involved in the degradation of proteins, which stimulate the activity of PAR-2 receptors (protease-activated receptor) present in the epidermis and playing a central role in inflammatory and nociceptive processes. This activation subsequently induces the release of TNF-α and IL-1, inflammatory agents. These are responsible for the redness and inflammation observed in individuals suffering from rosacea.

Cause No. 3: Heat.

Heat is suggested to contribute to the development of inflammations observed in cases of rosacea. It would also exacerbate irritations and hot flushes associated with the disease. Indeed, the TRVP1 receptors of the epidermis, involved in nociceptive mechanisms, activate in response to a thermal stimulus.

Cause No. 4: Stress.

Significant stress could also contribute to intensifying rosacea. This would act on the TRPA1 and TRVP1 receptors. After stimulation of these receptors located at the level of sensory neurons, certain neuropeptides, such as PACAP and CGRP are released. These act on the blood vessels causing vasodilation, which is the origin of the redness and persistent erythema found in rosacea. It can be assumed that cortisol, the hormone released in times of stress, interacts directly or indirectly with these receptors. However, the mechanism by which cortisol would act has not been elucidated.

Cause No. 5: The UVB rays from the sun.

UVB rays account for 5% of the UV radiation received on Earth. They are highly energetic and can penetrate the epidermis, causing sunburn, allergic reactions and even skin cancers. UVB rays are likely to interact with the TRVP4 receptors in the epidermis, which are partly responsible for the deterioration of skin tissues under the effect of the sun. The stimulation of these receptors triggers nociceptive mechanisms and a change in the structure of the skin.

Cause No. 6: Certain foods.

Just as with heat, the capsaicin, found particularly in chilli, bell pepper and pepper, is capable of stimulating the activity of the TRVP1 receptor, causing the dilation of blood vessels. This phenomenon is partly responsible for the hot flushes and irritations experienced by individuals suffering from rosacea.