What are the effects of the sun on acne?

Exposing oneself to the sun during the summer season to treat acne may seem like sound advice. Indeed, UV rays and heat accelerate dehydration and dry out the skin. As a result, it becomes less oily, presents less sebum on the surface, and the pores become less quickly clogged. Furthermore, when the skin tans, it thickens to better protect itself from UV rays. In other words, it establishes a protective barrier against the sun. As the skin surface is thick and pigmented, red marks and imperfections are less visible.

Even though these effects have been clearly demonstrated in the short term, it has also been proven that the sun's UV rays have a detrimental impact on acne in the medium to long term.

The drying effect of the sun on acne spots is temporary, as is its action on the sebaceous glands responsible for sebum production. At the start of the summer season, sun exposure can give the appearance of beautiful skin. However, following the drying phase, the skin system re-establishes itself, leading to a reactive hyperseborrhea. Consequently, the sebaceous glands produce an astronomical amount of sebum that attempts to surface on the skin. As the skin is thick, the pilosebaceous follicles become blocked and sebum accumulates in the pores. This build-up of sebum also promotes the growth of bacteria responsible for the onset of acne. Following prolonged sun exposure, acne outbreaks occur as the skin surface thins to regain its normal thickness. This is known as the rebound effect.

Furthermore, UV rays also damage skin cells and cause mild redness or more or less painful sunburns. If we add to this an increased risk of skin cancer, deeper wrinkles and other harmful effects, it is generally better to avoid excessive sun exposure, even if it is to alleviate acne over just a few days!

Exposure to the sun of scars left by acne tends to darken post-inflammatory marks further. Indeed, the area that contained the acne spot has a damaged surface that produces an increased amount of melanin. This overproduction is established to protect the skin from UV rays. Thus, persistent brown spots will be even more visible on the surface.

Some active ingredients prescribed to alleviate acne are photosensitising: they increase the skin's sensitivity to the sun's UV rays. This is, for example, the case with retinoids (chemical compounds derived from vitamin A) and benzoyl peroxide. In addition to their photosensitising aspect, these compounds can dry out the skin and reduce the horny layer: the skin's sensitivity to sunburn is thus further exacerbated. Therefore, apply these molecules to your skin in the evening and protect yourself from the sun's rays the following day with a suitable skincare product.

To select a sunscreen that will adequately protect your skin, always opt for products offering a broad-spectrum protection. This way, the care in question shields against both UVA and UVB rays, which are associated with sunburn, skin cancer, and signs of premature ageing.

Next, one must select a sunscreen with a sun protection factor (or SPF) that is suitable for their skin type. Thus, fair skin should opt for sun protection with an SPF of 50 or more, while for darker to black skin, an SPF of 30 will suffice.

Finally, if you suffer from acne, the choice of a sunscreen that is non-comedogenic can make all the difference. Non-oily and non-comedogenic formulas are lightweight and do not clog your pores, thus limiting the occurrence of blackheads.

For instance, you could use our face sun cream SPF50 with aloe vera. Its fluid and light texture makes it optimal for oily and acne-prone skin, although it remains suitable for all skin types. Moreover, it contains hyaluronic acid to hydrate the skin while protecting it.

• WILLIAMS H. C. & others. Epidemiology of acne vulgaris.British Journal of Dermatology (2012).