Blocking or enhancing effects of some basic emollients in UVA penetration

Abstract: Background: Topical agents used in combination with phototherapy or photochemotherapy may have both blocking or enhancing effects in ultraviolet rays. Objective: In this in vivo study, the effects of topical petrolatum, basis cream, glycerine, and olive oil on the transmission of ultraviolet A radiation were investigated. Methods: A test was performed to determine the minimal phototoxic dose on 29 volunteers with only psoralen plus ultraviolet A (PUVA) and then the same test was repeated with white petrolatum, basis cream, glycerine, olive oil, and sunscreen (0.3cc/25cm2). The effects of each agent on the minimal phototoxic dose were determined after 72 h. Results: When compared to pure PUVA, there was a statistically significant increase in the mean minimal phototoxic dose values by the application of white petrolatum (P = 0.011), but there was no significant increase or decrease in the mean minimal phototoxic dose values after the application of basis cream (P = 0.326), glycerine (P = 0.611) or olive oil (P = 0.799). Study limitations: Low number of patients Conclusion: The application of white petrolatum, which has a blocking effect, and also of basis cream immediately before PUVA therapy should not be recommended. Although we specify that glycerine and maybe olive oil can be used before photochemotherapy, there is a need for further research in larger series.

Protection of UV-radiation induced skin toxicity by reactive oxygen scavengers.

Although, photoaddition reactions of psoralens with DNA and membrane lipid are regarded as the major photochemical events responsible for skin-photosensitization and photochemotherapeutic properties, their O2-dependent reactive oxygen specie (ROS) generating potential is also responsible for biologic photooxidation reactions and cutaneous phototoxicity. We have investigated the skin-sensitization reactions of psoralen in presence of selected free radical scavengers. The results confirm that sodium azide, DABCO and beta-carotene inhibited considerably the 1O2 generation reactions in a chemical system (determined by monitoring the bleaching of N,N-dimethyl-p-nitrosoaniline in the presence of histidine used as a selective acceptor of 1O2) as well as skin sensitization in vivo (epilated guinea pig skin). These observation suggest that the O2-dependent photodynamic action of psoralen contributes significantly to the development of cutaneous toxicity which can be inhibited by selective scavengers of 1O2.