Polymorphous Light Eruption, Rash, Sun Exposure, Ultraviolet (UV) Light, Sunscreen, Teledermatology



  1. Matzek, Carmen
  2. Brodell, Robert T.
  3. Nahar, Vinayak K.


ABSTRACT: While there are a number of skin rashes associated with photosensitivity, only one produces a distinctive rash with fixed urticaria, macular erythema, and papulovesicles forming small papules and plaques. This polymorphous light eruption requires aggressive broad spectrum UV protection, topical steroids for pruritus, and paradoxically sometimes UV light treatment to "harden" the skin making skin more resistant to rashing when exposed to the sun.


Article Content


Chief complaint: Rash.


A 31-year-old businessman presented with a 48-hour history of a rash on the hands and forearms (Figures 1 and 2). He reported traveling 4 hours in a car several days ago returning from a weekend trip to the beach. He notes he was in the sun for a few hours and that he wore a hat, a short sleeve shirt, and long pants to protect himself from ultraviolet (UV) light.

Figure 1 - Click to enlarge in new windowFIGURE 1. A 1 x 1 cm erythematous plaque with a rim of macular erythema studded with fine papules is noted over the left 5th knuckle while only macular erythema is noted over the left 4th knuckle.
Figure 2 - Click to enlarge in new windowFIGURE 2. Erythematous macules and plaques are accentuated over the knuckles, but macular erythema is also noted on sun exposed skin on the back of the hand typical of the many forms of rashing seen in polymorphous light eruption.

* Prior treatment: None, and the patient was taking no medications.


* Prior biopsy: None.


* Skin history: No history of similar rashes or any medical problems. No history of skin disease.


* No other significant laboratory/study findings.




Two images provided showed a dozen 5- to 20-mm diameter clustered papulovesicular lesions on the extensor knuckles and on the dorsal forearms.



Fully satisfactory.




Polymorphous light eruption (PMLE) may show any combination of pinpoint or larger papules, vesicles, and/or erythematous macules on sun-exposed skin after UV exposure in light-skinned individuals. The rash can be asymptomatic, although it is most often pruritic. It occurs when individuals first are exposed in the springtime or when traveling to the beach. After repeated exposures, "hardening" occurs (Schweintzger et al., 2015). The pathophysiology of this process is not completely understood, but regulatory T-cells from patients with PMLE lack the capacity to suppress effector T-cell proliferation induced by sun exposure. This situation is reversed after effective treatment.




* Skin care recommendations: The patient was instructed to use a broad-spectrum (UVA/UVB blocking) sunscreen with SPF 30 or greater when exposed to the sun, especially in the first exposures in the springtime.


* Medication recommendations: None.




* Refer to dermatology clinic for evaluation (face-to-face) and consideration of a skin biopsy if the lesions do not fade over several weeks while avoiding the sun.



PMLE is a common immunologically mediated photodermatosis that occurs in temperate climates. The variable appearance of pruritic skin lesions occurs most commonly in the spring or early summer on sun-exposed areas (Gruber-Wackernagel et al., 2014). Making this clinical diagnosis and recommending broad-spectrum UV avoidance and protection will most often lead to prompt resolution without further treatment or diagnostic testing (Bissonnette et al., 2012).


The differential diagnosis includes a photosensitive reaction to drugs, although this patient was not taking any photosensitizing medications. An allergic contact dermatitis could be considered, although linear streaking was not present in any area (Kimber et al., 2002). Dermatitis herpetiformis can appear as grouped papulovesicles, but the excoriations and predominant elbow and knee distribution of this condition is not present here (Antiga et al., 2019). Solar urticaria fades more quickly than these fixed lesions (Botto & Warshaw, 2008).


In many patients, PMLE fades over days to several weeks without treatment. Patients with significant pruritus are treated effectively with oral and topical steroids (Ling et al., 2017). Phototherapy with narrow-band UVB, UVA, and PUVA can induce "hardening" and may help patients with recalcitrant disease (Ling et al., 2017). Several natural remedies have been recommended for PMLE including B-carotene and nicotinamide 2-3 g daily. The latter was shown to lead to resolution of all symptoms in 60% of patients in an uncontrolled trial of 42 patients (Lembo & Raimondo, 2018).




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Botto N. C., Warshaw E. M. (2008). Solar urticaria. Journal of the American Academy of Dermatology, 59(6), 909-920. [Context Link]


Gruber-Wackernagel A., Byrne S. N., Wolf P. (2014). Polymorphous light eruption: Clinic aspects and pathogenesis. Dermatologic Clinics, 32(3), 315-334. [Context Link]


Kimber I., Basketter D. A., Gerberick G. F., Dearman R. J. (2002). Allergic contact dermatitis. International Immunopharmacology, 2(2-3), 201-211. [Context Link]


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Ling T. C., Dawe R. S., Gardener E., Rhodes L. E. (2017). Interventions for polymorphic light eruption. The Cochrane Database of Systematic Reviews, (10).[Context Link]


Schweintzger N., Gruber-Wackernagel A., Reginato E., Bambach I., Quehenberger F., Byrne S. N., Wolf P. (2015). Levels and function of regulatory T cells in patients with polymorphic light eruption: relation to photohardening. British Journal of Dermatology, 173(2), 519-526. [Context Link]


1 The standardized teledermatology reader report format is available for authors on the journal's Web site ( and on the submissions website online at [Context Link]