To the Editor.—
During the past decade, we have successfully used a sunscreen containing dihydroxyacetone/ naphthoquinone (lawsone) for patients with all types of cutaneous photosensitivity.1 An advantage of this sunscreen is its capacity to induce a broad "ultraviolet shield" (290 to 405 nm) in the uppermost layer of the skin. In order to induce ultraviolet protection, the patient's skin must have an intact keratin layer. The amount of photoprotection achieved by a patient depends upon the following: (1) the chemical reactivity of the skin with the sunscreen; (2) the thickness of the keratin layer; (3) the number of applications of the sunscreen per day; (4) the degree of the patient's photosensitivity; and (5) the quanta of light per unit time received by the patient. Because of these variables, there is a wide spectrum of protective responses in our study1 from less than one hour to more than eight
Fusaro RM, Johnson JA. Dihydroxyacetone Naphthoquinone Sunscreen. JAMA. 1972;222(13):1651. doi:10.1001/jama.1972.03210130043021
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