Sun ‘Allergies’ & Photosensitivity
Photosensitivity is the abnormal reaction of skin to light and sunlight, often referred to as a ‘sun allergy’. Its incidence in childhood is rare, but it is during childhood that some of the more severe ‘sun allergies’ (photosensitivity disorders) can first occur, causing children and parents great distress.
Generally a ‘sun allergy’ is neither an allergy, nor caused specifically by the sun. These disorders can be caused by a range of factors; some environmental, some chemical and others unknown. For most photosensitivity disorders, a particular wavelength of light is responsible, such as visible light or invisible ultraviolet (UV) radiation. A child may be sensitive to a specific type of radiation (the longer wavelength, UVA, is most common) or to a broad range. Symptoms of photosensitivity vary considerably, but commonly include sunlight-induced rashes (photodermatoses), skin reddening and blisters or lesions.
Causes of photosensitivity
Diseases which can cause photosensitivity in children include:
- A variety of skin disorders, called photodermatoses, including – solar urticaria, hydroa vacciniforme, actinic prurigo and polymorphic light eruption (PLE)
- Genetic skin disorders, such as the rare disease xeroderma pigmentosum
- Metabolic conditions – the most common of these are the porphyrias, where photosensitising chemicals (porphyrins) build up in the skin (see more on EPP, one of the more common porphyrias to present in children)
- Underlying skin disease, such as eczema (atopic dermatitis) or psoriasis, can sometimes be exacerbated by sun exposure
Other potential causes of photosensitivity:
- Some medicines contain substances which can photosensitise the skin of susceptible people; be sure to mention to your doctor or dermatologist any medications your child might be taking
- Contact with specific plants, dyes, fragrances or other chemicals can also induce photosensitivity
Diagnosis and treatment
Assessment of a suspected photosensitivity by a dermatologist includes a description of patient/family history and a physical examination. The clinician may then require laboratory tests (such as blood, urine and faecal tests) and skin biopsies or phototests (measured tests of the skin’s response to light) to determine the cause. The specific precautions necessary and treatments available will depend on the individual condition diagnosed or the stimulus of the photosensitivity. Many people with a photosensitivity do need to avoid excessive sun exposure, though the degree varies.
Parents who believe the sun is definitely the issue should seek a referral to a physician or dermatologist who specializes in photosensitivity disorders (such as a photodermatologist), as many children go undiagnosed or misdiagnosed due to the rarity of these conditions and the difficulty of identifying UV or light as the cause.
Garzon, MC & DeLeo, VA 1997, ‘Photosensitivity in the pediatric patient’, Current Opinion in Pediatrics, 9(4):377-387.