The manifestations of rosacea differ vastly depending on the subtype. There are four major subtypes of rosacea:  erythematotelangiectatic rosacea (ETR), papulopustular rosacea (PPR), phymatous rosacea, and ocular rosacea.12 Patients with ETR present with flushing and telangiectasia of the face, usually accompanied by burning or stinging pain. Those with PPR have erythema of the face, so-metimes accompanied by burning or stinging pain. Phymatous rosacea manifests as thickened skin and nodules, most often on the nose. The features of ocular rosacea include conjunctivitis, iritis, scleritis, and other forms of ocular inflammation.11

Despite the different manifestations of the four subtypes, all types of rosacea can be treated topically with azelaic acid, metronidazole, or sodium sulfacetamide with sulfur. Because rosacea is commonly exacerbated by sun exposure, avoidance of sunlight and proper protection from the sun should be recommended.13


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Drug-induced photosensitivity

Numerous drugs can cause rashes in a photodistributed pattern after exposure to solar radiation. These photosensitivity reactions are subdivided into phototoxic and photoallergic reactions. Phototoxic responses occur within minutes to hours after the first exposure to a drug and appear as sunburn-type reactions, with erythema, hyperpigmentation, dermatitis, or blisters. Photoallergic responses are delayed reactions that occur on secondary exposure to a drug and appear as an itchy, erythematous rash that can manifest in numerous different forms, to include papules or vesicles.14

Systemic medications known to cause photosensitivity reactions include many antibiotics, antipsychotics, chemotherapeutic medications, diuretics, and anti-inflammatory drugs. The reaction induced by these medications is a phototoxic response. The diagnosis can be made after a careful evaluation of the patient’s medications. The rashes disappear when the drug is no longer taken.5

Photosensitive reactions can be induced by applying to the skin substances such as the chemicals in antibacterial solutions, sunscreens, and perfumes. These reactions are typically photoallergic and manifest as an itchy rash in a photodistributed pattern. The diagnosis can be made through a photopatch test, in which the skin is exposed to the specific ingredient and then to sunlight. If the specific allergen cannot be identified and the reaction is relentless, the patient may have to be treated with immunosuppressive medications.15

Polymorphic light eruption

Polymorphic light eruption (PMLE) is a delayed-type hypersensitivity reaction to UV radiation. It is a relatively common disorder that typically occurs in girls and young women, usually in fair-skinned individuals.16 The etiology of PMLE is unknown. The condition usually develops in individuals experiencing their first yearly prolonged exposure to sunlight.5 The resulting pruritic rash is described as polymorphous because it can manifest as almost any type of lesion, to include papules, plaques, or vesicles. The rash occurs on sun-exposed areas of the body and disappears on its own within two weeks. The differential diagnosis for PMLE includes solar urticaria, atopic dermatitis, and rare inherited photosensitivity diseases. The diagnosis can be made through the patient’s medical history or with phototesting. PMLE can be prevented with adequate sun protection. After the development of PMLE, corticosteroids can be used to accelerate the recovery process. Some patients with chronic PMLE may benefit from a course of phototherapy before a season of sun exposure.16

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Solar urticaria

Solar urticaria is a rare disorder in which a rash develops after exposure to sunlight. The rash initially appears as erythema on sun-exposed areas but then takes the form of raised hives. Solar urticaria is associated with intense pruritus. This is an immediate reaction that can be very severe. Rare cases associated with swelling of the mucosal membranes and difficulty breathing have been reported. The differential diagnosis for solar urticaria includes SCLE, drug reactions, porphyria, and PMLE. Solar urticaria can be diagnosed through phototesting. The most effective treatment is strict protection from the sun, to include the use of UVA- and UVB-blocking sunscreens. With limited success, phototherapy in stepwise doses has been used in patients to decrease the solar reaction. Other treatments include immunosuppressive medications and plasma exchange.5

Conclusion

In this article, we have reviewed six of the most common classes of conditions and diseases associated with photosensitivity: the porphyrias, lupus erythematosus, rosacea, drug-induced photosensitivity, polymorphous light eruption, and solar urticaria.

When a patient presents with a rash on sun-exposed areas, a thorough history must be taken that includes exposure to sunlight, use of medication, and prior personal and family history of manifestations of dermatologic disease.  The dermatologic examination further delineates the photosensitive dermatosis. Correctly diagnosing the specific condition associated with a photosensitive rash makes it possible to provide adequate treatment and, depending on the diagnosis, avoid future outbreaks. Clinicians must be aware of the spectrum of photosensitivity diseases because these conditions are common and can be associated with systemic diseases, although they are rarely life-threatening.

Young Moon and Danielle Brown are medical students and Maura Holcomb, MD, is a dermatology resident at Baylor College of Medicine in Houston. 

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