Sunscreens, used in the prevention of sunburn and skin cancer, have been commercialized since the 1930s. Their utilization is expanding, particularly in response to photoaging and an increase of skin cancer. However, failures occur in sunscreen use because their efficacy depends on the adequacy of application and utilization. This overview documents issues in sunscreen use and also discusses 2007 FDA-proposed rules to offer possible options for enhanced efficacy and communications to the consumer.
Ions play a crucial role in skin homeostasis. Calcium, a participant in wound healing and keratinization, is localized at an increasing gradient from the stratum basal to the stratum granulosum. In vivo and in vitro studies show disturbances in this gradient in damaged skin. We developed here a model to study ex vivo calcium outward flux from normal and tape-stripped human skin. We measured here, with a calcium specific electrode, ex vivo calcium percutaneous eggression from dermis to epidermis in normal and tape-stripped skin places in franz cells, with a calcium source or not in the dermis compartment. Tape-stripped skin released a greater calcium concentration and had a higher rate over time than normal skin in both cases. The rate went from 8.1.10(-3) ± 8.9.10(-3) nmol.cm(-2).min(-1) to 4.8.10(-2) ± 1.8.10(-2) nmol.cm(-2).min(-1) with no calcium in the dermis compartment and from 1.7.10(-1) ± 1.2.10(-1) nmol.cm(-2).min(-1) to 5.9 ± 3.4 nmol.cm(-2).min(-1) with calcium. Also calcium uptake from the dermis is greater in tape-stripped skin during the first 5 h of the experiment. This ex vivo method reproduced the increased of calcium skin permeability with a disrupted barrier. This approach aims to develop a non-invasive method to measure calcium flux concentration in normal and damaged skin that might be reproduced and validated in vivo.
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