Cosmetic ingredients that can trigger a purge.

This phenomenon of purging is typically due to the use of treatments that stimulate cellular renewal, which promote the skin's natural exfoliation. The microcomedones that are formed or in the process of forming will therefore all emerge at once. Among the ingredients that stimulate cellular renewal and/or exfoliate the skin, we find:

• Theazelaic acid.

  Azelaic acid is neither an AHA, BHA, nor a PHA, but its effect on the skin is comparable to that of a chemical exfoliant. Instead of breaking the bonds between the skin's surface cells, like chemical exfoliants, azelaic acid acts on the various stages of keratinisation, a cellular differentiation process that transforms cells from the deeper layers of the epidermis into dead cells to form the horny layer.

  Gentle on the skin, this natural dicarboxylic acid indeed possesses anti-keratinising capabilities, meaning it aids in normalising the keratinisation of the epidermis with a marked reduction in the thickness of the horny layer by modulating the early and terminal phases of the epidermal differentiation of keratinocytes. This can then trigger a skin purge.

• Organic Hydroxy Acids (AHA, BHA, PHA).

  Popular in cosmetic and dermatological formulas, hydroxy acids are known for their exfoliating properties on the skin. They gradually disrupt the cohesion of the corneocytes in the skin barrier, promoting the detachment of dead cells from the outermost layers of the stratum corneum in a uniform manner. Therefore, they accelerate the skin renewal cycle. Being water-soluble, AHA and PHA only act on the skin's surface, whereas BHA, which are fat-soluble, act on both the surface and deep within the pores. It is therefore not surprising that they carry a risk of skin purging.

  Terminology: glycolic acid, lactic acid, mandelic acid, citric acid, tartaric acid, malic acid, salicylic acid, betaine salicylate, willow bark extract, salicylate, trethocanic acid, sodium salicylate, lactobionic, gluconolactone.

• Enzymatic exfoliants.

  Fruit/yeast enzymes operate on the same principle as AHAs, BHAs, and PHAs. Their aim is to eliminate damaged skin cells that have accumulated on the upper layer of the epidermis and stimulate skin cell renewal through a chemical reaction. This is why they are associated with the purging phenomenon.

  Designations: grapefruit extract, pomegranate extract, raspberry extract, blackberry extract, papain, ficin, bromelain, actinidin, catalase, etc.

• Benzoyl peroxide.

  Commonly used in the form of a cream or gel in the treatment of acne, benzoyl peroxide has three functions: an antibacterial action that aims to eliminate the bacteria involved in the inflammatory phenomena of acne (Propionibacterium acnes), a moderate sebostatic action to regulate sebum production and a keratolytic action to neutralise hyperkeratinisation. This latter makes it another ingredient that triggers skin purging.

• The retinoids.

  Highly favoured for combating visible signs of ageing, pigmentation spots and acne, retinoids promote the proliferation and differentiation of epithelial cells (keratinisation process). Although the use of retinoids is accompanied by peeling due to their drying nature, they do not act on the surface like exfoliants.

  Liposoluble, retinol reaches the basal layer of the epidermis, where it penetrates into the keratinocyte to bind to a receptor in order to influence the secretion of transcription and growth factors, responsible for the proliferation of the epidermal layer and the strengthening of the protective function of the epidermis. Therefore, it can cause a skin purge when you start using it.

  Terminology: retinol, retinoic acid and its derivatives (tretinoin, adapalene, tazarotene, isotretinoin), retinal, retinol esters (retinyl palmitate, retinyl propionate, retinyl linoleate, retinyl acetate).