How to Choose and Use Sunscreen Correctly?

What does SPF mean?

SPF is primarily a measure of protection against UVB-induced erythema. It does not indicate UVA protection or visible light protection on its own.

SPF 30 or 50?

For most daily use, SPF 30 or higher may be sufficient. For intense sun exposure or a tendency towards pigmentation, SPF 50+ is often preferred. Higher SPF doesn't completely compensate for insufficient application.

Does SPF 100 provide twice the protection of SPF 50?

No. There is no linear relationship between SPF and UV blockage. Sufficient amount and regular reapplication are important.

What is the difference between UVA and UVB?

UVB is closely associated with sunburn and direct DNA damage. UVA reaches deeper layers of the skin; it is important for photoaging and pigmentation. Both can contribute to the risk of skin cancer.

How can I tell if I've received UVA protection?

According to the labeling system, indicators such as broad spectrum, UVA logo, PA, UVA-PF, or PPD may be used. Not only SPF but also UVA protection should be evaluated.

How long should it be applied?

Laboratory SPF tests are performed with an application rate of approximately 2 mg/cm². For the face, a product approximately two finger lengths long is recommended in practice; the amount should be increased if both the face and neck are to be protected.

How often should it be reapplied?

With intense outdoor exposure, replenishment is needed approximately every two hours; sooner after swimming, sweating, or drying with a towel. The needs of someone who works in an enclosed office all day are not the same as someone who is at the beach.

What is the difference between mineral and chemical sunscreens?

More accurate terms are inorganic/mineral filters and organic filters. Zinc oxide and titanium dioxide are mineral filters. Modern organic filters can also be effective. Mineral products have not been shown to be healthier for all patients.

What to choose for sensitive skin?

Products that are fragrance-free, have limited irritant content, don't dry out the barrier, and are well-tolerated are preferred. Sometimes mineral filters are better tolerated; sometimes products with organic filters can be used without problems.

What should be chosen for acne-prone skin?

Lightweight, non-comedogenic products that don't leave a greasy feeling may be more comfortable. However, the most important thing is that the person uses the product in sufficient quantity and regularly.

Is sunscreen selection different for melasma?

Yes. In melasma, not only ultraviolet light but also visible light can increase pigmentation. Tinted sunscreens containing iron oxide can provide additional protection against visible light and may be advantageous in those with a tendency towards melasma/post-inflammatory hyperpigmentation (PIH).

Are all tinted sunscreens the same?

No. Visible light protection varies depending on pigment density, iron oxide content, and formulation. The word "Tinted" alone doesn't mean all products are equivalent.

Can makeup replace SPF?

Generally, no. Most people don't apply makeup in the amount recommended for SPF testing. Makeup can be applied over sunscreen.

What does "waterproof" mean?

This means it maintains a certain degree of protection after being exposed to water for a specific period. No sunscreen is completely waterproof; it should be reapplied after swimming and heavy sweating.

Does it cause vitamin D deficiency?

Sunscreen theoretically affects vitamin D synthesis because it reduces UVB. A 2025 systematic review/meta-analysis reported a small mean decrease in 25(OH)D levels, but studies were heterogeneous. Discontinuing sun protection is not a recommended approach to preventing vitamin D deficiency; the risk of deficiency should be clinically assessed and managed with diet or supplementation as needed.

What is the best sunscreen?

This is a broad-spectrum product suitable for different skin types, which can be used regularly and in sufficient quantities. A lightweight, fluid formula might be more suitable for acne-prone individuals, a moisturizing cream for dry skin, a tinted product containing iron oxide for melasma, and a water-resistant product for athletes.

When choosing a sunscreen, the focus should not be on the product that theoretically offers the highest protection, but rather on one that provides adequate UVA/UVB protection and can be used regularly in the correct amount. Visible light protection should also be considered for those prone to melasma and pigmentation.

Dermatologist's Perspective