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Causes de la rosacée.

What are the causes of rosacea?

Rosacea is a chronic skin condition affecting nearly 415 million people worldwide. It manifests as excessive redness, typically appearing around the age of 40 and concentrating on the central part of the face, avoiding the area around the eyes and mouth. While the exact causes of rosacea remain unclear, several avenues are currently being explored by scientists. Let's discover them together in this article.

Summary
Published January 22, 2024, by Pauline, Head of Scientific Communication — 7 min read

How does rosacea manifest itself?

The characteristic symptom of rosacea is the presence of a widespread and diffuse redness on the face. This typically concentrates around the nose, cheeks, chin and forehead. The small blood vessels are also apparent and particularly visible on the fairest skin types. Rosacea is also accompanied by numerous invisible symptoms, such as significant skin sensitivity, burning sensations and tingling around the affected areas.

This skin disease tends to progress over time and operates in cycles. Thus, symptoms manifest for weeks or months, then may disappear before reappearing more strongly. Indeed, while rosacea initially causes redness, more severe symptoms can emerge over time, such as red pus-filled bumps, significant skin thickening, or even eye involvement.

Four subtypes of rosacea have been identified.

  • Vascular rosacea or thread veins.

    This is the most common form of rosacea. It primarily induces hot flushes, temporary or permanent redness known as erythema, heightened skin sensitivity, and the dilation of vessels beneath the skin, becoming visible.

  • Papulopustular rosacea.

    It is sometimes mistaken for acne due to the presence of red spots, or even pustules, in addition to redness. Papulopustular rosacea is also accompanied by feelings of tightness and sensations of burning and discomfort.

  • Hypertrophic rosacea.

    This rare form is characterised by a thickening of the skin and a dilation of the skin pores on the nose, referred to as "rhinophyma". This is a major complication of rosacea, due to the aesthetic damage it causes. The skin thickening is sometimes associated with papulo-pustules and can extend to the rest of the face.

  • The Ocular Rosacea.

    Rosacea sometimes affects the eyes. In such cases, patients exhibit redness of the eyelids, conjunctivitis, and dry eyes. Often, they also suffer from a persistent sensation of having grains of sand in their eyes.

It is crucial to consult a dermatologist at the first signs of symptoms. Mild rosacea can quickly lead to complications, particularly affecting the eyes.

What causes 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 appear to promote the dilation of blood vessels, a key element of rosacea.

  • 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 this phenomenon is not yet fully explained.

  • A 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 interleukin-1 (IL-1), inflammatory agents. These are responsible for the redness and inflammation observed in individuals suffering from rosacea.

  • The heat.

    Heat is suggested to contribute to the development of inflammations observed in cases of rosacea. It also exacerbates 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.

  • Stress.

    Significant stress could also contribute to intensifying rosacea. It would act on the TRPA1 and TRVP1 receptors. Upon 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 flushing 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.

  • 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 an alteration of the skin structure.

  • Some 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.

Sources

  • Thèse de Kelly ZAROUKIAN. Étude des aspects cliniques cellulaires et moléculaires de la rosacée, des traitements dermo-cosmétiques associés ainsi que de l’impact sur la qualité de vie des patients (2017).

  • STEINHOFF M. & al. Recent advances in understanding and managing rosacea. F1000 Research (2018).

  • TAN J. & al. Rosacea: new concepts in classification and treatment. American Journal of Clinical Dermatology (2021).

  • ALI F. & al. Rosacea. British Journal of Hospital Medicine.(2021).

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