Albino hairless mice (Skh:HR-l) exposed to sub-erythemal doses of UVB or UVA radiation display physical, visible, and histological alterations. Skin surface replicas, transepidermal water loss, and skin fold thickness were found to change with irradiation. Visibly, the skin wrinkled with UVB and sagged with UVA exposure. These changes were graded on 3-point scales. Histological alterations included tissue thickening, loss of elastic fibers, elastosis, loss of collagen, and increases in muco-substances. The UVB alterations occur to a much lesser extent with an SPF-15 (7% PABA and 3% oxybenzone) sunscreen product. This sunscreen product had little effect on development of UVA-induced changes. However, an efficient UVA sunscreen (Parsol 1789) did reduce the UVA-induced changes. Many of the UVB-induced alterations regressed after UVB irradiation was stopped. No regression in UVA-induced alterations was observed when UVA irradiation was stopped. Qualitatively, the effects with UVA irradiation were like those observed in mouse chronological aging. These models and the convenient physical and visible grading methods described can be used to determine the effectiveness of topical treatments, such as sunscreens.
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