Prevention of Polymorphic Light Eruption Afforded by a Very High Broad-Spectrum Protection Sunscreen Containing Ectoin

Abstract

Introduction: Polymorphic light eruption (PLE) is the most common idiopathic, acquired photodermatosis. The pathophysiology of PLE is not yet fully understood but seems to involve immunological mechanisms, UVA-induced oxidative stress, and the subsequent elicitation of a cellular stress response affecting keratinocyte gene expression and skin immune function. In the present study, a high broad-spectrum sunscreen medical device (MD), containing a very high protection complex of UVB and UVA filters and ectoin, was investigated for its ability to protect against UVA-induced PLE.

Methods: The study was carried out as a monocentric, double-blinded, randomized, untreated controlled design. The test MD was applied (2 mg/cm²) on one side of the chest according to a randomization list of 15 patients with a typical history of PLE, and the contralateral area remained untreated. After product application, the test areas were exposed daily to increasing doses of UVA radiation (from 40 to 60 J/cm²) until a PLE reaction was detected or for a maximum of five consecutive days. Evaluations of induced PLE included clinical scoring and chromametry for erythema and pigmentation.

Results: Overall, no positive PLE reaction was observed on the side of the chest treated by the test MD, whereas positive PLE reactions were triggered on the untreated side of 13 subjects. Subjective sensations were very rare on the MD-treated side but were numerous and more severe on the untreated side. Chromametry and clinical visual inspection indicated that the skin color was unchanged on the MD-protected side, whereas high increased values of erythema and pigmentation were observed on the untreated chest side.

Conclusion: This MD sunscreen based on a complex of UVA-UVB filters and 1% of ectoin may be effective in preventing UVA-induced PLE. New studies comparing this MD sunscreen versus the same product without ectoin should be conducted.

Clinicaltrials: gov identifier: NCT05320315 (retrospectively registered 09/17/2021).

Keywords: Ectoin; Polymorphous light eruption; Sunscreen.

Fig. 1

Cumulated number of subjects who did not develop a positive reaction over time

Fig. 2

PLE worst severity scores observed during the study

Fig. 3

Worst subjective scores observed during the study

Fig. 4

a Chromametry parameter a* over time. Error bars represent standard error of mean (SEM). Double stars (**) indicate significant difference (p < 0.001). b Chromametry parameter ITA over time. Error bars represent standard error of mean (SEM). Double stars (**) indicate significant difference (p < 0.001)

Fig. 5

Comparison of the protected chest side (left) versus the unprotected chest side (right) for one subject. PLE reaction is clearly visible on the unprotected side, whereas no reaction is observed on the protected side