Sunscreen labels are easy to misread, and plenty of people find them confusing. The American Academy of Dermatology (AAD) points to a study published in JAMA Dermatology in which fewer than half of the patients at a dermatology clinic knew the meaning of terms like "broad spectrum" and "SPF". The numbers do measure real things, just not always the things people assume.
SPF tells you how much UVB light, the burning rays, a sunscreen can filter out. According to the AAD, SPF 15 filters out 93% of the sun's UVB rays and SPF 30 filters out 97%. Higher SPFs block slightly more, but no sunscreen blocks 100%. The AAD also points out that high-number SPFs last the same amount of time as low-number SPFs, so a bigger number doesn't buy extra time outdoors without reapplying.
Most people do not apply enough sunscreen, says the NHS. The AAD notes that many people only apply about 20 to 50% of the amount needed to achieve the SPF on the label, and the NHS adds that if sunscreen is applied too thinly, the protection it gives is reduced.
UVA is a separate question. A 2026 study of 38 sunscreens rated SPF 50 or higher, selected from Europe, Latin America, Oceania and Asia, notes that SPF is primarily a measure of UVB protection and does not quantify protection from UVA. Their measured UVA protection factor ranged from 3.6 to 46.6, and only 26 of the 38 met the EU recommendation. The authors found a lack of relationship between SPF and UVA protection. A high SPF, in other words, tells you nothing reliable about UVA. Countries also differ in how they test and label UVA protection. In the UK, the NHS advises looking for at least 4-star UVA protection, or the letters "UVA" in a circle, which indicates the product meets the EU standard. Whatever UVA mark your bottle carries, read it separately from the SPF.
For the face alone, the AAD suggests at least 1 teaspoon, about the amount needed to cover the length of your index and middle fingers. For skin not covered by clothing, most adults need about 1 ounce, roughly enough to fill a shot glass. Outdoors, it advises reapplying every two hours, and straight after swimming or sweating.
this contact form is a decent place to start if you want product-specific advice rather than general labels, since formulations differ between mineral and chemical filters. The AAD's definition is simple: if the active ingredient is titanium dioxide, zinc oxide or both, it's a physical (mineral) sunscreen; if it contains neither, it's a chemical one. All of them form a protective layer that absorbs the sun's rays, and physical sunscreens also reflect them. Dermatologists recommend mineral sunscreens for people with sensitive skin.
Storage matters too. The AAD advises against leaving sunscreen in direct sunlight or somewhere hot such as inside a car, because this speeds up the rate at which the ingredients break down. It also says the FDA requires sunscreens to keep their original strength for at least three years, that an expired sunscreen should be thrown out, and that if a bottle has no expiry date you should write the purchase date on it. Obvious changes in colour or consistency mean it's time for a new bottle.
For general daily wear, the AAD recommends a sunscreen that is broad spectrum (protecting against UVA and UVB), SPF 30 or higher, and water resistant.
Is all-natural the best type of acne therapy?
Sunscreen isn't an acne treatment, but the title asks a fair question about natural products, so here is what one trial of a natural remedy looks like: a 2009 study of a 2% green tea lotion. Twenty patients with mild to moderate acne applied it twice daily for 6 weeks. Their mean count of papules and pustules fell from 24 to 10, a reduction of 58.33%, and the mean severity index dropped from 2.05 to 1.25. The authors concluded the lotion is an effective, cost-effective treatment.
Read the design before the conclusion, though. The abstract describes 20 patients and no comparison group, so it can't show how much of that improvement would have happened anyway. That's a reason to call green tea interesting, not to call all-natural the best type of acne therapy.
If you have acne-prone skin, the label still matters. The AAD suggests a broad-spectrum, water-resistant sunscreen with an SPF of 30 or higher that says "non-comedogenic" or "won't clog pores", and notes that acne treatments may take several weeks to a few months to show a difference. The NHS suggests treatments such as salicylic acid or benzoyl peroxide with a pharmacist's advice, warns not to scrub your skin, as this can irritate it and make acne worse, and recommends seeing a GP if self-treatment isn't working.
If you're building a simple routine and want to know where a product fits before spending on it, read more about how we source and vet what we recommend, or get in touch with specific questions about your skin type.
This article is general information, not medical advice. If acne is severe, scarring or not improving, speak to a pharmacist, GP or dermatologist.
References
- American Academy of Dermatology. How to decode a sunscreen label. aad.org
- American Academy of Dermatology. Sunscreen FAQs. aad.org
- American Academy of Dermatology. How to apply sunscreen. aad.org
- NHS. Sunscreen and sun safety. nhs.uk
- Young A, Tricaud C, Bernerd F, et al. In vivo measurement of UVA protection factor (ISO 24442:2011) across 38 different SPF 50 and SPF 50+ sunscreens reveals high heterogeneity and limitations in the level of protection. Photodermatol Photoimmunol Photomed. 2026;42(3):e70092. PMID 41968398
- Patel MN, Patel N. Global perspectives on regional sun protection factor (SPF) requirements: scientific and regulatory insights. Cureus. 2026;18(2):e103757. PMID 41869094
- Elsaie ML, Abdelhamid MF, Elsaaiee LT, Emam HM. The efficacy of topical 2% green tea lotion in mild-to-moderate acne vulgaris. J Drugs Dermatol. 2009;8(4):358-64. PMID 19363854
- American Academy of Dermatology. Acne: Tips for managing. aad.org
- NHS. Acne. nhs.uk/conditions/acne