Eczema and sun: good or bad idea?

Individuals suffering from eczema are not all equal when it comes to the sun. While some notice an improvement in their skin condition with the arrival of warmer weather, others see their lesions worsen. This is referred to as photosensitive eczema. This is a photo-allergy, meaning a cross-reaction between a product containing an allergenic molecule and the sun's UV rays. It's quite rare, but it does happen.

Phototherapy is sometimes recommended for individuals suffering from eczema. This method utilises UV rays to alleviate the red lesions and characteristic itching of this skin condition. Numerous studies demonstrate its positive effect on eczema . One study, in particular, showed that regular exposure of 29 children to UVB with a restricted range of wavelengths (300-320 nm) for 12 weeks resulted in a 61% reduction in their SASSAD (Six Area Six Sign Atopic Dermatitis) score. This score is often used to measure the severity of eczema.

Another point in favour of the sun: it stimulates the synthesis of Vitamin D . A recent study has shown that Vitamin D increases the production of cathelicidins. These are molecules that act against Staphylococcus aureus, bacteria that sometimes colonise eczema-prone skin. Staphylococci can cause secondary infections of eczema, sometimes with significant consequences. Vitamin D has a protective effect against this. Furthermore, it promotes the production of proteins necessary for the functioning of the skin barrier, which limits dryness and the entry of pathogens.

Despite the various elements mentioned above, it is quite challenging to determine the effect of the sun on eczema. Indeed, phototherapy is different from direct sun exposure. When one exposes oneself to the sun, it is without medical supervision. Moreover, natural UV rays have a much broader wavelength range than that used in phototherapy. As for vitamin D, sun exposure is not the only way to obtain it for the body. It is possible to take it orally via dietary supplements.

Finally, even though the sun provides certain benefits, it's important not to forget that it can also prove to be harmful to the skin and cause skin problems other than eczema (sun spots, melanomas, premature skin sagging...). To avoid these, it's crucial to apply a broad-spectrum sun care product, that is, one that protects against both UVA and UVB rays, before each exposure, even if you have eczema. Opt for a cream with a rich texture, which can nourish your skin in addition to protecting it from the sun.

• TAYLOR A. & al. Narrowband ultraviolet B phototherapy in children with moderate-to-severe eczema: a comparative cohort study. The British Journal of Dermatology (2014).

• PALMER D. Vitamin D and the Development of Atopic Eczema. Journal of Clinical Medicine (2015).