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Glossary 

# UVA

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## Definition

UVA (Ultraviolet A) rays are the longest wavelength of ultraviolet radiation (320-400 nm) emitted by the sun. They account for approximately 95% of the UV radiation that reaches the earth's surface and are present at relatively equal intensity throughout the day and year — even on cloudy days and through window glass. UVA rays penetrate deep into the dermis, where they damage collagen and elastin fibers, generate free radicals, and contribute to photoaging (premature wrinkles, sagging, and age spots). UVA rays also play a significant role in skin cancer development and can worsen hyperpigmentation conditions like melasma. Unlike UVB rays, UVA exposure does not cause an immediate visible sunburn, which makes it deceptive — the damage occurs silently over time. Protection against UVA requires broad-spectrum sunscreen with ingredients like avobenzone, zinc oxide, tinosorb, or mexoryl. The PA+ rating system (used in Asian sunscreens) specifically measures UVA protection.

## Related Terms

[UVB](/glossary/uvb)[Broad Spectrum](/glossary/broad-spectrum)[SPF](/glossary/spf)[Sunscreen](/glossary/sunscreen)[Free Radicals](/glossary/free-radicals)

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[Definition](#definition)[Related Terms](#related-terms)

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[UVB](/glossary/uvb)[Urea](/glossary/urea)

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