Rosacea: everything you need to know about this skin condition.

Rosacea is a chronic skin disorder that affects the face, primarily the forehead, nose, cheeks, and chin. It is characterised by the presence of a widespread and extensive redness, rosacea also causes the dilation of small blood vessels in the face, which tends to make them visible. Other symptoms often accompany rosacea, such as hot flushes, skin hypersensitivity, as well as 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 pus-filled red bumps, significant skin thickening, or even eye involvement.

Rosacea is the cause of various symptoms, ranging in severity. The initial manifestations of rosacea are often mild but it can subsequently progress into a more serious condition. Four subtypes of rosacea are identified.

• Vascular rosacea or couperose.

  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.

• The 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.

• The 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 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.

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.

• The genetics : It is estimated that about 30% of people with rosacea have a family history of this condition, leading researchers to believe that unidentified genes may be involved. One hypothesis being considered is the prevalence among people suffering from rosacea of certain receptors, mentioned below, involved in inflammatory mechanisms.

• A Parasitic Colonisation : The Demodex, parasites naturally found in the hair-sebaceous regions of the skin, secrete proteases that stimulate the activity of PAR-2 receptors (protease-activated receptor) present in the epidermis. 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.

• Heat : It also exacerbates irritations and heat flushes associated with the disease. Indeed, the TRVP1 receptors of the epidermis, involved in nociceptive mechanisms, activate in response to a thermal stimulus.

• The stress : It 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 blushing and persistent erythema found in rosacea.

• The UVB rays of the sun : Constituting 5% of the UV rays received on Earth, they are likely to interact with the TRVP4 receptors of the epidermis, partly responsible for the deterioration of skin tissues. The stimulation of these receptors triggers nociceptive mechanisms and a change in the structure of the skin.

• Certain foods : Just as heat, the capsaicin, found particularly in chilli and pepper, is capable of stimulating the activity of the TRVP1 receptor, causing the dilation of blood vessels.

The medical treatments for rosacea primarily aim to reduce symptoms and prolong the intervals between flare-ups, but they cannot completely cure it. Depending on the type of rosacea, the techniques vary.

• Alleviating Vascular Rosacea : redness can be reduced by using the laser. A gel containing brimonidine is sometimes prescribed for its vasoconstrictive effect.

• Alleviating Papulopustular Rosacea : a local treatment based on gel, cream, or lotion is generally prescribed. This often involves metronidazole, an antibiotic that also has anti-parasitic properties. The application of care enriched with azelaic acid is also recommended.

• Alleviating hypertrophic rosacea : only a surgical operation can restore the normal shape of the face.

• Alleviating Ocular Rosacea : eyelid massages using an antibiotic ointment are recommended to reduce ocular rosacea. Patients are also administered oral antibiotics and are given artificial tears to combat eye dryness.

If you suffer from rosacea, you can take some additional precautions to prevent rosacea flare-ups. The first instinct to adopt is to apply a sunscreen every morning with an SPF of at least 50.

Indeed, as previously explained, the UVB rays from the sun are likely to exacerbate rosacea. It is preferable to avoid exposure and to wear a hat if you must be in the sun. Another tip is to provide the skin with daily hydration. Applying a cream, particularly one containing hyaluronic acid, nourishes the skin deeply while protecting it against external aggressions and free radicals.

Finally, it may be prudent toadjust one's diet when suffering from rosacea. Studies have shown that spicy foods such as chilli or pepper can interact with certain skin receptors, triggering inflammatory mechanisms. It is also advised against consuming alcoholic beverages, spicy foods, or foods high in histamine (tomatoes, citrus fruits...) or in cinnamaldehyde (cinnamon) in case of rosacea. These tend to have a vasodilatory effect and can cause hot flushes and the appearance of redness.

On the contrary, the consumption of caffeine is recommended for its vasoconstrictive properties. Foods rich in vitamin B2 (green vegetables, rice...) or zinc (seafood, offal...) can also be favoured, as they are believed to stimulate certain signalling pathways that trigger anti-inflammatory mechanisms.

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• AL-NIAIMI F. & al. Rosacea and diet: what is new in 2021? Journal of Clinical and Aesthetic Dermatology (2021).

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