What is the difference between UVA and UVB protection?

UVA and UVB at a glance

Which UV rays cause sunburn?

UVB is the main cause of sunburn. Short periods of excessive sun exposure can leave skin hot, red and painful, with peeling a few days later. UVB also contributes to tanning and other skin damage. Burning is not the only consequence of too much sunlight, so avoiding a burn is only part of protecting your skin.3

Which UV rays cause skin aging?

UVA contributes to premature aging, including wrinkles, and damages deeper layers of skin. Repeated UV exposure also increases uneven pigmentation and skin cancer risk. Daily protection matters because exposure accumulates beyond beach days: skin meets daylight in cool weather and on cloudy days too, neither of which has read the holiday itinerary.34

Does SPF measure UVA protection?

No. SPF, short for sun protection factor, measures UVB protection. The number does not tell you the sunscreen's UVA protection. On UK sunscreens, look for SPF 30 or higher and at least four UVA stars. The star scale goes up to five, with higher ratings indicating better UVA protection. A UVA symbol inside a circle indicates that the sunscreen meets the EU standard. SPF is useful, but it is not the entire label doing its job.2

On US labels, look for the words broad spectrum, which mean the product meets requirements for protection against both UVA and UVB. Water resistance is a separate claim: 40 or 80 minutes describes how long the labeled SPF protection lasts during swimming or sweating. No sunscreen is waterproof, and water resistance does not remove the need to reapply.5

SPF 30 blocks about 97% of UVB rays; higher SPF values block slightly more, but none blocks all of them. Higher SPF does not last longer or let you skip reapplication. For sensitive skin, mineral sunscreen containing zinc oxide, titanium dioxide or both is an option. Chemical, mineral and hybrid formulas can all provide protection when they are broad spectrum, water resistant and SPF 30 or higher.1

How to get both types of protection

1. 1Check the label for SPF 30 or higher and UVA protection, and check the expiry date.
2. 2Apply generously to exposed skin, including your face, neck, ears and exposed scalp. Around 6 to 8 teaspoons is the UK guide for covering an adult's whole body; applying too thinly reduces protection.
3. 3For an outing long enough to risk burning, apply sunscreen 30 minutes before leaving and again just before going out.
4. 4Reapply every two hours outdoors and straight after swimming, sweating or towel drying. Reapply sooner if sunscreen has rubbed off, following the product's directions.

Do clouds and windows protect you?

Cloud cover does not switch UV exposure off: up to 80% of the sun's UV rays can get through clouds. Sun protection belongs in every season, not just hot weather. Water, sand and snow reflect UV radiation and increase exposure, so a cool setting can still require careful protection.5

Window glass blocks UVB but allows UVA through, so being behind glass does not remove every type of UV exposure. A tan is also no substitute for protection: tanning damages skin and increases the risk of premature aging and skin cancer.1

What else protects against UVA and UVB?

Sunscreen cannot completely block UV radiation. Add shade, clothing that covers exposed skin and a broad brimmed hat. Limit midday exposure: US advice highlights 10am to 2pm, while UK advice highlights 11am to 3pm. Avoid sunbeds and tanning lamps, which can deliver more dangerous exposure than natural sunlight.45

For your eyes, choose sunglasses labeled UV400 or 100% UV protection. These block more than 99% of UVA and UVB radiation. Large wraparound frames can offer more coverage, and UV absorbing contact lenses do not replace protective sunglasses.5

Who needs extra care?

People of every skin colour need protection. Be especially careful with pale skin, light or red hair, a personal history of skin cancer or a family history of it. Some medicines increase sun sensitivity, so ask your prescriber or pharmacist about precautions for your medication. Keep babies under six months out of direct sunlight and seek medical advice before applying sunscreen to them.25

If you receive prescribed UVA phototherapy, follow your treatment team's sun precautions. UVA treatment requires hospital supervision, and unnecessary sunlight exposure, including through window glass, should be avoided on treatment days. Tell the team about new medicines or creams because some increase light sensitivity. Contact the team if excessive redness develops after treatment.6

What if you burn or notice a skin change?

Cool sunburned skin and apply moisturiser or aftersun. Do not burst blisters or repeatedly touch the burn, because infection can follow. Severe sunburn can leave you more likely to burn again for several months. Seek urgent medical assessment if vomiting, fever or headaches develop after sun exposure.3

Stay out of the sun until redness has gone. Seek medical help for severe swelling, blistering or feeling unwell. Report a new or changing mole, growth or unusual spot to your doctor promptly rather than waiting for the next sunny season.24