How come our skin becomes darker after sun exposure, but things like packaging become lighter/bleached?
In:
Solar bleaching is mainly observed in non-living objects. Packaging and the like are not living.
Human skin usually gets darker due to sun exposure because the living cells (melanocytes specifically) react to UV exposure by producing the pigment melanin, which protects the skin from future UV exposure.
Skin has melanin pigments in it that actively adapt to lighting conditions over time to protect our skin from too much UV radiation from damaging the skin. Packaging is not living nor adaptive so there’s no response so sunlight can penetrate without difficulty and damage the structures and color of what’s there.
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