Pouvez-vous être allergique au soleil ?

Cases of photosensitivity can range from mild to severe - and milder cases are not always obvious.

"Développer des rougeurs de la peau est une réponse normale après une exposition excessive au soleil. Une sensibilité anormale à la lumière ou une allergie au soleil se produit lorsque la réponse d'une personne à la lumière du soleil dépasse les limites des sujets en bonne santé. Cela inclut le développement de rougeurs à des doses de lumière solaire plus faibles que la normale," explique le Dr Daniel Glass de The Dermatology Clinic London.

What is polymorphic light eruption?

Bien qu'il existe plusieurs types différents de photosensibilité, polymorphic light eruption (PLE) est le plus courant, et il peut se présenter de différentes manières.

"Polymorphe signifie plusieurs formes, ce qui signifie que l'éruption cutanée peut avoir de nombreuses apparences différentes. Le terme 'éruption lumineuse' signifie que éruption cutanée apparaît après une exposition au soleil. La LPE peut se manifester par de petites bosses rouges qui démangent, de plus grandes zones rouges et des cloques," explique Glass.

As well as direct sun exposure, the rash may occur if a person is exposed to sunlight through a glass window and even sometimes fluorescent lighting. It usually appears within a few hours of exposure, and may occur in as little as 20 minutes.

Une variante de l'éruption polymorphe à la lumière, appelée juvenile spring eruption, specifically affects the upper edges of the ears (the helices). It usually affects males in childhood or early adulthood and most often occurs in early spring. Classically, it's seen after strong sun exposure in relatively cold weather - later the same day, the helices become red and itchy, and a day or two later, blisters appear. Fortunately it tends to settle on its own within a couple of weeks. However, it's a good idea for people affected to wear a hat that covers their ears in spring and possibly summer for the next few years.

Who is affected?

Whilst photosensitivity may occur in people of any skin type, those with lighter skin are more commonly affected and especially a skin type known as: "Fitzpatrick skin phototype 1 - those people who have red hair, have freckles and burn easily in the sun," explains Glass. "It can affect anyone at any age, but is most common in women between the ages of 20 and 40 and tends to be more common at high altitude and in the spring."

Although the cause of the condition can sometimes be genetic, there are many other potential causes of photosensitivity.

"Certains médicaments et produits chimiques peuvent provoquer une sensibilité lorsqu'ils sont appliqués sur la peau ou pris par voie orale," explique Glass. "La liste des médicaments et produits chimiques pouvant causer une sensibilité à la lumière est longue et inclut divers antibiotiques, antifongiques, médicaments cardiaques et psychiatriques - pour n'en nommer que quelques-uns." Topical anti-inflammatory les crèmes et les gels peuvent également causer une photosensibilité.

Il est particulièrement important de garder à l'esprit le risque de photosensibilité si vous envisagez des comprimés de prévention antipaludique, qui sont presque exclusivement nécessaires dans les régions ensoleillées du monde. Doxycycline, un antibiotique proposé comme option pour la prévention du paludisme dans certaines régions, peut entraîner une photosensibilité.

What does the rash look like?

Whilst the rash may appear similar to sunburn, in the majority of cases it can be distinguished from burning by the initial presentation and progress of the rash.

"The most common rash is smooth-topped red bumps on the skin, which can coalesce into plaques. This is different to the classical flat red sunburn. The rash often persists for several days, clearing up without scarring if further sun is avoided. If the affected area is exposed to more sun the rash will get worse and spread," explains Glass.

What should I do?

If you're worried you or your child might be affected, it's best to talk things over with your GP, who will refer you to a dermatologist if necessary. Depending on the severity and your circumstances, a number of different treatments may be prescribed. Clearly, if you're taking any medication, it's important to speak with your pharmacist to see if that might be the cause. If it could be, see your GP - the solution might be as simple as stopping your treatment or changing to a different medicine.

"The rash can be treated with a corticosteroid cream or ointment, which may help it settle more quickly. Mild PLE may be controlled by sun avoidance and use of high-factor UVB and UVA sunscreen. More severe PLE may require oral steroids," explains Glass.

"In some cases, desensitisation treatment can be helpful. Desensitisation is a way of increasing the skin’s tolerance of sunlight by introducing slowly increasing doses of ultraviolet light in a special phototherapy cabinet. The treatment is started in early spring before the sun becomes strong enough to be problematic. The desensitisation needs to be repeated each year, supervised by a dermatologist."

Whilst photosensitivity can make enjoying the sun more difficult, taking precautions and getting the right treatment should prevent it from blighting your summer.