We all know that sunburn is to be avoided, but did you know that some skin conditions are made visible by sun exposure? These types of skin rashes are called Sun Sensitive Dermatoses. These conditions present on sun-exposed skin primarily. They may be triggered by exposures from topical products or oral agents and tend to resolve when sun exposure is avoided. Sometimes a genetic predisposition is present in an individual preceding a triggering event, which leads to a rash on sun-exposed sites. There are also photosensitive connective tissue disorders or nutritional deficiencies underlying a sun-exposed, site-specific rash. One thing they all have in common: SPF against both UVB and UVA is important as part of treatment. Let’s explore them more closely:1
1. Photosensitive drug eruptions: This may present as a sunburn (phototoxic) or a photoallergic (eczematous) rash. This type of eruption requires both ultraviolet exposure and ingested medication. Therefore, the rash may not first appear when the medication was first initiated making an inciting culprit more difficult to ascertain. Stopping the offending drug is the most important part of treatment. Some common causative medications are NSAIDs (non-steroidal anti-inflammatory drugs), tetracyclines, captopril, phenothiazines, quinidine, sulfonamides, thiazide diuretics, and sulfonylureas drugs.1
2. Polymorphous Light Eruption: This rash occurs mainly in the spring, then improves with the progression of summer and fall. This rash affects more women than men and occurs within the first 3 decades of life. Exposure to the sun in increments allows further tolerability to more exposure. Measures that can be taken to accrue sun exposure incrementally is to avoid the mid-day sun, seek shade when available, wear protective clothing and using sunblock. This diagnosis is largely a diagnosis of exclusion (meaning other diagnoses have been ruled out), but a biopsy is helpful.1,2
3. Chronic Actinic Dermatitis: These patients, usually men, respond abnormally to UV radiation. Itchy patches show up on areas exposed to sunlight, such as the neck, forearms, hands or the sides of the face. Surprisingly, this condition may occur in persons with dark skin also. A biopsy may be necessary to differentiate this skin disorder from another such as cutaneous T-cell Lymphoma.1
4. Porphyria Cutanea Tarda: This condition is due to a deficiency of an enzyme in the liver. People don’t usually know they have this deficiency until a trigger such as alcohol, estrogen or hepatitis C initiates a photosensitivity reaction on the skin. Painful, blistering and ulcerative lesions form in areas of sun exposure, such as the hands and arms. Laboratory investigation confirms the diagnosis. Phlebotomy is the mainstay of therapy. The first evidence of improvement is decreased skin fragility in sun affected sites.2
5. Lupus: Really all of the different kinds of cutaneous lupus are characterized by sun sensitivity on the skin. There are different forms of lupus, some of which are confined to the skin only such as discoid and subacute variants. Discoid is a scarring cutaneous disease. Systemic lupus often presents on the skin in the form of a “butterfly rash” and “photosensitivity.” The butterfly rash has been mistaken for rosacea, so if you have suffered from such a rash, come in for further evaluation.2
References:
1. Photosensitivity Dermatoses. Derm101.com website. https://www.derm101.com/therapeutic/photosensitivity-dermatoses/overview/ . Updated 2019. Accessed July 30, 2019.
2. Fleischer AB, Feldman SR, McConnel CF, Petrazzuoli M, Pardasani AG, Hess MR. Emergency Dermatology: A Rapid Treatment Guide. NewYork, NY: McGraw-Hill; 2002: 276-281
