Papules: How are these red bumps formed?

A papule is a full, dry bump measuring 0.5 to 5 mm in diameter that does not produce any fluid when punctured, unlike a pustule. These bumps have a pink to red color and adopt a more or less regular round shape. The papules can settle on any part of the body and are sometimes itchy. There are two types of papules: epidermal papules, which develop in the epidermis, and dermal papules, which are located in the dermis. Most often, papules are due to an inflammatory dermatosis, such as acne or rosacea, although some papules result from a viral infection, like chickenpox, shingles, or even papillomavirus infections, notably responsible for papules on the vulva.

The formation of a papule begins with a phenomenon of blockage at the level of the hair follicles and sebaceous glands. Two factors can cause this obstruction: hyperseborrhea, which is an increase in sebum production, and hyperkeratinization, or an abnormal multiplication of dead cells from the horny layer. An accumulation of sebum and/or corneocytes within the hair follicle is then observed, leading to an enlargement of the pore and the emergence of a pimple. These phenomena are primarily mediated by androgen hormones, which stimulate the activity of the sebaceous glands and keratinization.

Unlike a simple whitehead or blackhead, a papule appears in an inflammatory context.

This lipid-rich environment is conducive to the proliferation of Cutibacterium acnes, a bacterium naturally present on the skin. C. acnes thrives by digesting the triglycerides found in sebum and converting them into free fatty acids, which irritate the follicular walls. The presence of this bacterium and its byproducts triggers the activation of the immune response. Langerhans cells, the cells of skin immunity, recognize bacterial antigens and lipids produced by C. acnes through molecular pattern recognition receptors, such as Toll-like receptors 2 and 4 (TLR-2 and TLR-4). This recognition triggers the production of pro-inflammatory cytokines, such as interleukins 1 and 6 (IL-1 and IL-6) and tumor necrosis factor (TNF-α), as well as chemokines that attract immune cells to the papule. The clustering of neutrophils and T lymphocytes around the follicle amplifies inflammation in the surrounding tissues, resulting in redness and swelling around the blocked follicle, characteristics of a papule.

How to make a papule disappear?

The papules may disappear on their own over time without intervention, but there are solutions that can speed up this process. First and foremost, it is important to keep the skin clean by washing it twice a day and avoiding touching the papule, as this could lead to an infection. Treatments with benzoyl peroxide or sulfur can also help to dry out the papule and combat inflammation. Moreover, benzoyl peroxide has exfoliating and sebostatic activities, allowing it to neutralize hyperkeratinization and hyperseborrhea. However, if you do not notice any improvement after six to eight weeks, if your papules multiply, or if they become a significant source of discomfort, it is recommended to consult a dermatologist.