Health effects
Knowledge Base articles tagged Health effects.
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The dangers of UVA radiation
UVA's health effects: photoaging and wrinkles, indirect DNA damage via reactive oxygen species, skin-cancer and melanoma risk, eye damage, immune suppression and photosensitivity — plus practical ways to cut exposure.
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UVA sunscreen labels decoded: PA+++, the UVA circle, stars and critical wavelength
SPF measures UVB almost exclusively. How to read actual UVA protection: the EU circled-UVA logo, the Japanese PA system, Boots stars, the US broad-spectrum test, avobenzone photostability, and which UVA filters are available where.
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How much sunscreen you actually need — and why UVA suffers most
Sunscreen is tested at 2 mg/cm² and applied at a quarter of that, and protection falls exponentially with thickness. Why under-application and photodegradation hit UVA protection hardest, plus the teaspoon and two-finger rules.
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UVA and your eyes: sunglasses, UV400, cataracts and pterygium
How UVA reaches and damages the eye, what UV400, EN ISO 12312-1 and ANSI Z80.3 actually guarantee, why dark lenses without UV filtering may be worse than none, and why frame shape matters more than lens darkness.
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UVA and skin aging: how photoaging actually happens
UVA reaches the dermis and drives the enzymes that dismantle collagen. The mechanism from photon to wrinkle, the trial showing daily sunscreen halts measurable aging, the evidence from truck drivers and twins, and what genuinely repairs the damage.
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Does UVA tan you? Tanning, burning and the base-tan myth
UVA darkens skin within minutes by oxidising melanin you already have — a tan that offers almost no protection. The three distinct tanning responses, why UVA barely burns, and what that means for tanning beds and the base-tan idea.
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UVA and vitamin D: all of the cost, none of the benefit
Vitamin D synthesis is driven by a narrow slice of UVB around 295–300 nm and stops entirely below 315 nm. UVA produces none of it — which makes winter sun, window light and sunbeds pure exposure with no return.
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UVA, melanin and pigmentation: melasma, hyperpigmentation and skin tone
UVA and visible light drive melasma and post-inflammatory hyperpigmentation far more than UVB — which is why tinted, iron-oxide sunscreens outperform clear ones. What melanin does and doesn't protect against, across Fitzpatrick types.
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Photosensitivity: medications and conditions that make UVA dangerous
Most drug photosensitivity is UVA-driven, which is why it happens through car and office windows and on overcast days. Phototoxic vs photoallergic reactions, the main drug classes, PMLE, lupus and porphyria, and what protection actually works.
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UVA indoors: nail lamps, tanning beds and what your lights really emit
Gel-manicure lamps are almost pure UVA, tanning beds emit heavily UVA-shifted spectra, and screens emit no UV at all. What each indoor source actually puts out, how it compares to midday sun in W/m², and where the real risks are.
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