The various forms of rosacea.

Rosacea manifests as a widespread and diffuse redness on the face , particularly on the forehead, nose, cheeks, and chin, due to the high vascularization of these areas. Rosacea is characterized by a significant dilation of the facial blood vessels, making them more visible, especially on lighter skin tones. These signs are often accompanied by skin hypersensitivity, hot flashes, as well as burning and tingling sensations.

Indeed, rosacea tends to progress over time. Its symptoms can disappear for a few weeks before suddenly returning in a more intense manner. In fact, the face can be affected by significant swelling, deformations, or papules. In the most severe cases, rosacea reaches the eyes and causes their inflammation.

The causes of this dermatological disorder are still poorly identified, however, several ongoing research studies have demonstrated that certain factors could be responsible for rosacea flare-ups. Notably, these include hereditary predisposition, parasitic colonization, heat, sun rays, stress, or the consumption of certain spicy foods. These various elements, apart from genetics, are capable of activating certain receptors present in the epidermis, which have nociceptive and/or inflammatory roles. It has thus been shown that exposure to one or more of the mentioned factors contributes to promoting hot flashes, redness, and sensations of irritation experienced by individuals affected by rosacea.

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 disorder. Four subtypes of rosacea are distinguished.

The condition of rosacea or vascular rosacea.

This form of rosacea is quite common. The first sign of rosacea is the gradual onset of diffuse redness, taking the form of patches on the face. The areas around the eyes and mouth are often spared. Initially, the redness disappears but, over time, it eventually becomes permanent. This is then referred to as erythrosis.

They are generally accompanied by intense hot flashes and increased skin sensitivity. In some cases, the natural peeling of the skin tends to be more pronounced and it becomes drier. Individuals suffering from rosacea often complain of burning and tingling sensations on the skin.

In the case of vascular rosacea, we also observe the emergence of small red or purplish blood vessels beneath the skin, a result of their dilation. Characteristic of this skin condition, they are referred to as telangiectasias. Occasionally, some skin swelling may also appear.

Papulopustular Rosacea.

This form of rosacea typically follows telangiectasia. It occurs due to the invasion of the parasite Demodex in the sebaceous glands. They are naturally present in the epidermis where they play a role in sebum regulation. However, when more than 5 parasites per square centimeter of skin are observed, it is considered a colonization.

The Demodex mites secrete proteases, enzymes involved in protein degradation, which stimulate the activity of PAR-2 receptors (Protease-Activated Receptor) that play a central role in inflammatory and nociceptive processes. This activation subsequently leads to the release of TNF-α and interleukin-1 (IL-1), which are inflammatory agents.

Beyond redness, heat flashes, and feelings of tightness, we observe in individuals suffering from papulopustular rosacea the emergence of skin lesions. This condition is sometimes mistaken for acne, as it also results in the appearance of papules, and in some cases, pustules.

Hypertrophic Rosacea.

This type of rosacea is a significant complication, due to the substantial aesthetic damage it causes. Quite rare, hypertrophic rosacea is characterized by a thickening of the skin, as well as dilation and inflammation of the nose pores, referred to as "rhinophyma". In some cases, the skin thickening is sometimes associated with papulopustules and can extend to the rest of the face.

Hypertrophic rosacea originates from an increase in the volume of the sebaceous glands. The causes remain somewhat unknown, but it is considered to be a strong inflammatory reaction triggered by the infectious agent Demodex. The nose is particularly affected, as this area contains a large portion of the sebaceous glands on the face.

Ocular Rosacea.

It is estimated that about 30 to 50% of rosacea cases are accompanied by ocular involvement. When it affects the eyes, this condition generates burning and itching. This eye condition is also characterized by inflammation and swelling of the eyelids. It is believed to be due to a dysfunction of its glands, the Meibomian glands.

Located at the base of the eyelids, they normally contribute to the lubrication of the eyes by secreting an oily substance. Ocular rosacea also causes a dryness of the eyes, which become red and teary. The eyes then become particularly sensitive to light. Small blood vessels dilate and become visible on the white area of the eye.

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

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• SEITZMAN G. & al. Ocular rosacea. Current Opinion in Ophthalmology (2020).

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