Why does retinol irritate the skin?

The retinol is used to improve many common skin issues, such as wrinkles and fine lines, blemishes, brown spots, dull complexion, and enlarged pores. Although it is an effective ingredient that will give you visible results within a few months, the topical application of retinol often causes unwanted effects , the most common of which is local irritation, clinically similar to a mild contact dermatitis. It can last between four to six weeks (retinisation), which is the time it takes for your skin to develop a tolerance.

During the initial phase of use, your skin acclimatises to the effects of retinol and may develop a slight irritation (retinoid dermatitis). The inflammatory response induced by retinol is somewhat delayed compared to the classic inflammatory events caused by other external stimuli. Various mechanisms are thought to be involved in the irritation induced by retinol. Indeed, this adverse reaction could potentially be associated with a widespread and pervasive inflammation, characterised by the release of pro-inflammatory mediators and the infiltration of immune cells, as well as a disruption of the skin barrier illustrated by a genetic imbalance of factors related to the stratum corneum. Indeed, a study has shown that retinoids induce an increase in the expression of MCP-1, IL-8, IL-12p40 and TNF-α in epidermal cells and fibroblasts, pro-inflammatory mediators responsible for the skin irritation induced by retinol.

Similarly, another study demonstrated changes in the morphology and structure of the epidermis following the application of retinoic acid. Specifically, the stratum corneum exhibited lipid droplets and abnormal cell-cell tight junctions, suggesting an alteration in lipid metabolism and dysfunctional cellular junctions. Indeed, they observed differential gene expression of factors associated with the epidermal barrier function (claudins, filaggrin, protease inhibitors, tissue kallikreins, etc.), as well as abnormal keratin maturation (parakeratosis) in a murine model and a keratinocyte cell line during skin irritation induced by retinoic acid. Furthermore, alterations in the balance between proteases and protease inhibitors in the skin lead to inflammatory reactions.

There are measures that you can take to prevent irritations associated with the use of retinol before they occur. However, it should be noted that even at low concentrations, a risk of irritation may arise.

• Opt for a retinol treatment containing anti-irritant actives: choose a formula with anti-inflammatory substances that have an inhibitory effect on the secretion of certain pro-inflammatory cytokines induced by retinol. In a recent study, researchers report the development of an anti-irritation formula guided by a genetic analysis, revealing the genetic factors that govern irritation induced by retinol. They propose a formula (glucosamine 0.1%, trehalose 2%, ectoine 2%, sucralfate 0.1%, omega-9 1% and 4-t-butylcyclohexanol 0.7%) that can modulate or mitigate the molecular pathogenesis induced by retinol in vitro. This new approach will allow retinol-based cosmetic products to be more accessible to sensitive skin and skin prone to retinol-induced irritation.

• Mixing retinol with a moisturising cream : you can also blend your retinol treatment with your moisturising cream. This will simultaneously hydrate the skin, while reducing the risk of irritation. Indeed, applying retinol at the same time as your moisturising cream allows it to be diluted without rendering it completely ineffective. This method can help your skin to develop a tolerance to retinol without causing irritation.

  Preferably look for a moisturising cream containing hyaluronic acid, ceramides, or glycerine.

• Adopting the "retinol sandwich" method: If you have dry or sensitive skin and wish to incorporate retinol into your skincare routine, you can opt for the "retinol sandwich". Layering topical retinol with a moisturising cream will help to temper any skin irritation. This involves applying a first layer of moisturiser just after washing your face, followed by the retinol on top, and sealing it all with a second protective layer.

• Opt for another form of retinoid : if you have particularly sensitive skin, prone to rosacea, or you want a gentler option, you might consider choosing a different type of retinoid (retinol esters, granactive retinol, etc.) which offers similar benefits but with a significantly lower risk of irritation.

• Switch to a simple skincare routine during the adaptation period: in order to reduce the risk of developing retinoid dermatitis, go back to basics and abandon masks, peels and exfoliating scrubs, especially if you have sensitive or dry skin. Indeed, avoid applying other products containing AHA, vitamin C or salicylic acid during retinisation.

• MAIBACH H. I. & al. The specificity of retinoid-induced irritation and its role in clinical efficacy. Exogenous Dermatology (2002).

• KANG K.-S. & al. The mechanism of retinol-induced irritation and its application to anti-irritant development. Toxicology Letters (2003).

• BERGE C. A. & al. Facilitating facial retinization through barrier improvement. Cutis (2006).

• LEE A.-Y. & al. Retinoic acid and hydroquinone induce inverse expression patterns on cornified envelope-associated proteins: Implication in skin irritation. Journal of Dermatological Science (2014).

• GENG S. & al. All‑trans retinoic acid alters the expression of the tight junction proteins Claudin‑1 and ‑4 and epidermal barrier function‑associated genes in the epidermis. International Journal of Molecular Medicine (2019).