image of silk fabric and dry skin

R. Bissonnette, MSc, MD, FRCPC

Division of Dermatology, University of Montreal Hospital Centre, Montreal, Quebec, Canada


Polymorphous light eruption (PLE) and solar urticaria (SU) are two photodermatoses that are induced by ultraviolet radiation and sometimes by visible light. This article will review the various means of preventing PLE and SU with an emphasis on the role of sunscreens.

Key Words:
PLE, polymorphous light eruption, solar urticaria

Polymorphous Light Eruption

Polymorphous light eruption is a common photodermatosis with a prevalence as high as 10-20% in Caucasian populations.1,2 Photo-provocation studies have shown that the eruption is triggered by UVA in most patients, although in certain patients UVB alone can trigger the eruption.3-5 In a recent series of 110 patients, PLE could be photoinduced with visible light in 23 patients who were also sensitive to UVB and UVA. The clinical significance of visible light sensitivity in these patients is unknown.6

Because PLE is a self-limited disease that spontaneously resolves when exposure to triggering light is stopped, the focus is centered on prevention. Sun protection and sun avoidance are central for PLE prevention. The level of photoprotection necessary to avoid the development of the eruption varies from patient to patient. For most patients with mild disease, avoidance of intense sun exposure, especially in the winter or early spring is sufficient to prevent the eruption. However, for some patients, seeking the shade and avoidance of intense sun exposure is not enough. Sunscreens have been recommended for these patients even though efficacy of earlier sunscreens has been low, probably because of their limited UVA protection.7

Sunscreen for the Treatment of PLE

We recently compared the efficacy of two high SPF sunscreens for the prevention of indoor PLE generated by metal halide lamps.8 The two sunscreens compared were Coppertone® 45 which contains only oxybenzone for UVA protection and Anthelios® L, which contains Mexoryl SX, Parsol® 1789 and titanium dioxide (TiO2) for UVA protection. UVA protection by oxybenzone is limited to short-wave UVA. Anthelios® L prevented PLE in all patients, whereas Coppertone® 45 was able to prevent PLE in only 3 patients out of the 23 who completed the study.

To further explore UVAprotection afforded by sunscreens we compared the ability of 6 sunscreens with SPF of 21 or more to prevent pigmentation induced 2 hours after artificial UV exposure.9 The sunscreens compared were: Anthelios® L 60, Bain de Soleil® 25, Coppertone® 45, Hawaiian Tropic® 50, Presun® 21 and Presun® 30. In order of decreasing efficacy the best sunscreens for UVA protection were Anthelios® L, Presun® 30, PreSun® 21, Bain de Soleil® 25, Coppertone® 45 and Hawaian Tropic® 50. In this study the two sunscreens that afforded the highest UVA protection contained Parsol® 1789, which has a maximal absorption at 358nm. Anthelios® L also contained Mexoryl SX for UVA protection, which has a maximal absorption at 345nm. The two sunscreens containing physical agents only (i.e., PreSun® 21 and Bain de Soleil® 25) were not as efficient for UVA protection, which could be related to the fact that the spectral protection of micronized titanium dioxide (TiO2) decreases with increasing UVAwavelength.10 This study confirmed that SPF, a measure of UVB protection, is not indicative of UVA protection provided by sunscreens. It also illustrates how difficult it is to select a sunscreen with broadspectrum and high UVA protection, since SPF is the only indicator of UV protection on sunscreen labels in North America.

Photostability is another important parameter to consider when selecting a sunscreen that provides good UVA protection. Parsol® 1789 is known to be photounstable in certain preparations.11 Unfortunately, it is not possible to know if a sunscreen is photostable only by looking at the label, because there is no information on this subject on labels in North America.

Prophylactic Treatments

Prophylactic treatments with UVA, UVB or PUVA therapy can prevent PLE in certain patients.12,13 Although PUVA therapy is effective, its use has to be weighed against the risks of squamous cell carcinoma and melanoma.14Atopical formulation containing the antioxidants tocopheryl acetate, ferulic acid and α-glycosylrutin was reported to prevent the development and reduce the severity of indoor PLE in certain patients,15 suggesting that the role of antioxidants in sunscreen formulations deserves further study.

Solar Urticaria

Solar urticaria (SU) is photodermatosis characterized by urticarial papules and plaques appearing typically after 5-10 minutes of sun exposure, with spontaneous disappearance after a few hours of sun avoidance. The spectrum of solar urticaria induction varies according to patients and can include UVA, UVB as well as visible light. Visible light alone can induce SU,16,17 and a recent Japanese series reported that as many as 60% of patients were sensitive to visible light.18

SU and Sunscreens

SU is a problem as far as sunscreens are concerned, because the protection afforded by sunscreens in the visible range is not very good. The absorption spectrum of chemical sunscreen agents is limited to the UV range of the solar spectrum. Although opaque nonmicronized physical agents may reduce visible light transmission, patients are reluctant to use opaque sunscreens. An in vitro spectroscopic study suggested that sunscreens with iron oxide offer a better protection against visible light than titanium dioxide or zinc oxide.19 RVPaque® is a sunscreen containing 1.7% of iron oxide.19 The disadvantage of iron oxide is that it gives a red-brown colour to sunscreens. Dihydroxyacetone can also protect against the lower portion of the visible spectrum.20 Many sunless tanning lotions contain dihydroxyacetone. With the current developments in the field of photodynamic therapy, which consists of administering drugs that make patients sensitive to visible light, there is renewed interest in the development of sunscreens that offer better protection in the visible range.

RankSunsreenSPFActive Ingredient
1Anthelios L® (LaRoche-Posay)60
  • Mexoryl SX
  • Parsol® 1789
  • TiO2
  • Parsol® 1789
  • TiO2
  • ZnO2
4Bain de Soleil®25
  • TiO2
  • ZnO2
  • Ethylhexyl P-Methoxycinnamate
  • Oxybenzone
  • 2-Ethylhexyl Salicylate
  • Homosalate
6Hawaiian Tropic®50
  • Octocrylene
  • Octyl Methoxycinnamate
  • Octyl Salicylate
  • TiO2

Table 1: Six sunscreens with SPF ratings >21 in order of decreasing efficacy tested to
prevent pigmentation induced 2 hours after artificial UV exposure.9

Other Treatments for SU

Antihistamines can be valuable for SU, but their use is often disappointing for patients with severe disease. Other treatments that have been used with limited success include UVB, narrow band UVB and PUVA therapy.21,22 Plasmapheresis has been used in selected cases with success.23 This approach is useful for patients, in which it is possible to induce urticarial plaques following in vitro irradiation of their own serum, suggesting that the improvement could be related to removal of the antigen by plasmapheresis. Interestingly, this modality has been shown to induce remissions of more than a year in certain patients.


In conclusion, PLE and solar urticaria can be prevented in most patients by decreasing their amount of sun exposure and by using an adequate sunscreen. As UVA is mainly involved in the induction of both diseases, the sunscreen used should contain broad as well as high UVA protection.


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