Common misconception: the sun makes acne disappear

Acne is a common skin condition, primarily associated with inflammation of the hair follicles and sebaceous glands. It manifests as comedones (blackheads and whiteheads), papules, pustules, and even nodules or cysts in severe cases. This condition results from a combination of factors, notably an excessive production of sebum, follicular hyperkeratinisation, bacterial colonisation (notably by Cutibacterium acnes) and local inflammation.

During adolescence, acne is triggered by a hormonal disturbance causing an overproduction of sebum. The excess sebum will grease the skin and block the pores, resulting in the formation of blackheads and the proliferation of acne-causing bacteria. Acne typically subsides with age, but it can persist due to a hormonal imbalance or skin predisposed to breakouts (oily or acne-prone skin, etc.).

Among the many myths and misconceptions surrounding acne, it is often said that sunlight makes acne disappear. This belief stems from numerous accounts of individuals who have noticed an improvement in their acne during the summer months. In fact, in some cases, a reduction in the formation of acne lesions can be observed.

Initially, moderate sun exposure can temporarily improve the appearance of acne-prone skin. Ultraviolet (UV) rays have an anti-inflammatory effect, reducing local inflammation around lesions. Moreover, the resulting tan visually masks certain redness and blemishes, giving the impression that acne is diminishing. Some studies highlight this temporary anti-inflammatory effect of UV rays on acne lesions. Moreover, sunlight stimulates the synthesis of vitamin D, which plays a role in regulating the skin’s immune system.

However, because of the drying resulting from sun exposure, the skin will initiate a reactive hyperseborrhoea to preserve its hydration. The sebaceous glands then begin to produce more sebum. As a result, a resurgence of acne occurs after the summer, around September and October. This is known as the rebound effect. Prolonged or excessive sun exposure can have deleterious effects on acne. UV rays may induce a hyperkeratinisation of the hair follicles, which promotes pore blockage and lesion aggravation. Furthermore, sun exposure triggers cutaneous oxidative stress, promoting a chronic inflammation that can exacerbate acne.

It is therefore important to warn about these side effects and to recommend appropriate photoprotection to prevent the deterioration of acne-prone skin.

A study conducted in 2018 on 110 patients aged over 25 years with common acne aimed to identify the aggravating factors of this skin condition. The researchers collected detailed data on age at acne onset, its duration, type, family history, and the potential impact of diet, cosmetics, medicines or sun exposure. The results revealed that 26.4% of participants reported a worsening of their acne following sun exposure.

Acne-prone skin warrants special attention, as it is naturally sensitive to sunlight. This sensitivity is often caused by the use of acne treatments, such as retinoids or certain antibiotics, which render the skin more sensitive to UV. It is therefore essential to apply rigorous sun protection to avoid sunburn, post-inflammatory hyperpigmentation and exacerbation of lesions.

Thus, sunlight has no beneficial effect on acne; on the contrary.

A skin prone to acne must be protected from the sun. To achieve this, it is recommended to apply sun creams with an SPF of at least 30 (ideally SPF 50), depending on skin type and duration of sun exposure. However, the sunscreen used on acne-prone skin should be labelled “non-comedogenic”. Indeed, certain ingredients in sunscreens can be comedogenic and may therefore promote the development of acne lesions and blackheads.

Although the cream protects the skin from the sun’s harmful effects, acne-prone skin can become sensitised by acne-fighting treatments. Therefore, it is recommended to limit sun exposure by staying in the shade whenever possible or by wearing covering clothing (wide-brimmed hat, long garments, etc.).

• SARKAR R. & al. Seasonal variation in acne vulgaris--myth or reality. The Journal of Dermatology (2002).

• WATSON A. & al. A systematic review of the evidence for 'myths and misconceptions' in acne management: diet, face-washing and sunlight. Family Practice (2004).

• SRIDHARAN R. & al. Factors Aggravating or Precipitating Acne in Indian Adults: A Hospital-Based Study of 110 Cases. Indian Journal of Dermatology (2018).

• KRUTMANN J. & al. Sun exposure, a relevant exposome factor in acne patients and how photoprotection can improve outcomes. Journal of Cosmetic Dermatology (2023).