General information only, not medical advice. If you have a skin condition, a history of skin cancer or concerns about a mole, see a doctor or dermatologist.
This guide is for someone who wears sunscreen on holiday but rarely otherwise, and who stands in the pharmacy aisle unsure whether SPF 30 or SPF 50 matters, what “broad spectrum” means, or whether last summer’s half-used bottle is still good. Perhaps you have started a simple skincare routine and want sun protection to be part of it, or you are buying for children for the first time. Sunscreen works well when you choose the right kind and use enough of it, and most people fall short on the second point.
What sunscreen protects against
Sunlight includes ultraviolet (UV) radiation. The US Food and Drug Administration’s guide to sunscreen and sun protection explains that UV radiation consists of both UVA and UVB. UVB is the main cause of sunburn; UVA penetrates deeper and contributes to skin ageing. Both contribute to skin cancer risk.
Reading the label
SPF
The FDA explains that a sunscreen’s SPF value is primarily an indicator of the level of protection against UVB radiation. Higher SPF means more UVB protection, but the FDA also warns against a common misunderstanding: some people believe that if they normally burn in one hour, SPF 15 lets them stay in the sun for 15 hours. That is not how it works. Sun intensity varies through the day, and sunscreen rubs, sweats and washes off.
Broad spectrum
Broad spectrum sunscreens help protect against both UVA and UVB. The FDA notes that not all sunscreens are broad spectrum, so it is important to look for that description on the label. The FDA advises using broad spectrum sunscreens with SPF 15 or higher regularly and as directed.
Water resistant
Products labelled water resistant must pass required tests, and the FDA says their labels must state whether the sunscreen remains effective for 40 or 80 minutes when swimming or sweating. No sunscreen is waterproof.
Expiry date
FDA regulations require non-prescription drugs, including sunscreen, to carry an expiry date unless stability testing shows they last at least three years. A sunscreen without an expiry date should be considered expired three years after purchase. Heat can degrade it faster, so do not leave bottles in a hot car.
| Label term | What it tells you | What to look for |
|---|---|---|
| SPF | Level of UVB protection | 15 or higher per FDA; many people choose 30 or more for long outdoor days |
| Broad spectrum | Protects against UVA and UVB | Must be on the label |
| Water resistant (40 or 80 minutes) | How long it lasts while swimming or sweating | Choose for sport or swimming |
| Expiry date | When it may stop working as labelled | Replace if expired or older than three years without a date |
SPF tells you about sunburn protection. Broad spectrum is what covers UVA too.
Choosing a formula
Sunscreens come in two broad types, and both can be effective.
Mineral sunscreens
These use zinc oxide or titanium dioxide. Many people with sensitive skin find them gentler. Older formulas left a white cast; newer ones are much sheerer.
Chemical sunscreens
These use organic filters that absorb UV. They tend to feel lighter and rub in clear, which suits daily wear under make-up.
Textures
Lotions suit body and dry skin. Gels suit hairy areas and oily skin. Sticks are handy for faces and children. Sprays are convenient but easy to under-apply; spray until skin glistens, then rub in, and avoid inhaling.
The best sunscreen is the one you will wear every day. If you dislike the feel of one, try another.
How much to apply
Most people use far less than the amount used in SPF testing, which means they get less protection than the label suggests. A common guide used by dermatologists is about a shot-glass amount, roughly an ounce, to cover the exposed body of an adult, and about a nickel-sized amount, or a generous half teaspoon, for the face and neck.
Easily missed spots
- Ears, including the tops
- Back of the neck and hairline
- Tops of the feet
- Backs of the hands
- Scalp along a parting
- Lips, using an SPF lip balm
When to apply and reapply
The FDA advises reapplying sunscreen at least every two hours, and more often if you are swimming or sweating. Follow the label directions, which all sunscreens must include.
Practical timing
- Apply before going outside so it is on when exposure starts
- Reapply after swimming, towelling off or heavy sweating, even if the product is water resistant
- Reapply every two hours during long days outdoors
Daily use under make-up
For a typical office day, sunscreen applied in the morning as the last step of skincare covers the commute and lunchtime. If you spend long periods outdoors, reapply. SPF in foundation alone is rarely enough, because people do not apply foundation thickly enough to match the tested SPF.
Sunscreen is one part of sun protection
The FDA’s key sun safety tips go beyond the bottle:
- Limit time in the sun, especially between 10 a.m. and 2 p.m., when the sun’s rays are most intense
- Wear clothing that covers exposed skin, such as long-sleeved shirts and trousers
- Wear sunglasses and broad-brimmed hats
- Use broad spectrum sunscreen of SPF 15 or higher regularly
Shade, clothing and hats do not wear off, which makes them reliable partners to sunscreen.
Children and babies
The FDA says sunscreen is not recommended for infants under six months old. It advises keeping infants out of the sun, particularly between 10 a.m. and 2 p.m., and using protective clothing if they must be in the sun. For older children, apply sunscreen generously, use hats and sun-protective swimwear, and plan outdoor play outside the midday peak where possible. Ask a paediatrician if your child has sensitive skin.
Storing sunscreen
Heat and sunlight can break sunscreen down. The FDA suggests protecting sunscreen by wrapping containers in towels or keeping them in the shade when you are outside in the heat for long periods. At home, store it somewhere cool. If a product has changed colour, separated or smells odd, replace it.
Common misunderstandings
- “I don’t need it on cloudy days.” UV passes through cloud, so you can burn on an overcast day.
- “Darker skin doesn’t need sunscreen.” Darker skin has more natural protection against burning but can still be damaged by UV.
- “A base tan protects me.” A tan is a sign the skin has already been damaged by UV.
- “One application lasts all day.” The FDA’s guidance is to reapply at least every two hours.
Building it into a routine
A simple daily routine makes sunscreen automatic:
1. Cleanse
2. Moisturise, if you use one
3. Apply sunscreen to face, neck and ears
4. Make-up, if you wear it
Keep a small bottle or stick in your bag or desk for reapplying, and a larger bottle by the door for summer.
Sunscreen checklist
- Broad spectrum on the label
- SPF 15 or higher, per FDA guidance; higher for long outdoor days
- Water resistant (40 or 80 minutes) for sport or swimming
- Not expired, and not older than three years if undated
- Enough applied: about a shot glass for the body, a generous half teaspoon for face and neck
- Ears, neck, feet and hands covered
- Reapplied at least every two hours, and after swimming or sweating
- Hat, sunglasses and covering clothing in strong sun
- Midday sun limited, especially for children
- No sunscreen for babies under six months; shade and clothing instead
Takeaway
Choose a broad spectrum sunscreen of SPF 15 or higher, as the FDA recommends, use enough to cover every exposed area, and reapply at least every two hours or after swimming. Treat it as one layer of protection alongside shade, hats and clothing, and check the expiry date each spring.
