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Photostability refers to the ability of a sun protection product to maintain its effectiveness when exposed to UV radiation. Over time, exposure to UV radiation can cause a breakdown of the active ingredients in sunscreen, reducing its ability to protect the skin.  
Our clinical testing service evaluates the photostability of a product in terms of UVA+B %RE (percentage of Residual Efficiency), which measures the amount of UVA and UVB protection that remains after exposure to UV radiation.  
This allows cosmetic companies to market their products with reliable, scientific evidence of their ability to provide long-lasting protection against harmful UV radiation. Products with high photostability are especially important for individuals who spend prolonged periods outdoors, as they can provide more consistent and reliable protection throughout the day.

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