Papules: How are these red bumps formed?

A papule is a full, dry spot ranging from 0.5 to 5 mm in diameter that does not produce any fluid when punctured, unlike a pustule. These spots have a pink to red colour 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: hyperseborrhoea, that is, an increase in sebum production, and hyperkeratinisation, which is 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 spot. These phenomena are primarily mediated by androgen hormones, which stimulate the activity of the sebaceous glands and keratinisation.

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 grows 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 by-products triggers the activation of the immune response. Langerhans cells, the cells of skin immunity, recognise the 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 tumour 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. Firstly, it is important to keep the skin clean by washing it twice a day and avoiding touching the papule, as this could cause an infection. Treatments with benzoyl peroxide or sulphur can also help to dry out the papule and combat inflammation. Moreover, benzoyl peroxide has exfoliating and sebostatic activities, allowing it to neutralise hyperkeratinisation and hyperseborrhoea. However, if you notice no 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.