We know that we need sun protection. Yet, we still don’t use it enough. Despite the world’s obsession with skincare, a recent report from PubMed showed that only 11 percent actually apply sunscreen
For reference, data from the American Academy of Dermatology (AAD) indicate that one in five Americans (a truly alarming percentage) will develop skin cancer in their lifetime. And, according to medical experts, one way to prevent it is to use sunscreen correctly.
So, it wouldn’t hurt to once again discuss how to choose a product with SPF, as well as how much and how often to apply it.
What to look for when choosing sunscreen
Most of us are familiar with the Sun Protection Factor (SPF)—the large number on the front of a sunscreen bottle. The higher the number, the more protection it provides. Many brands also indicate a five-star rating, which is equally important to understand.
SPF indicates how well the sunscreen protects against ultraviolet radiation. The star system shows what percentage of UVA radiation is absorbed by the sunscreen compared to UVB radiation.
What are UVA and UVB?
Ultraviolet A and B radiation are different wavelengths of solar radiation that reach the Earth’s atmosphere.
- UVA is associated with skin aging and pigmentation, as well as skin cancer, especially squamous cell carcinoma (the second most common type). It can affect human skin, even through glass.
- UVB causes sunburn and is associated with specific types of skin cancer — basal cell carcinoma (the most common type) and malignant melanoma.
Sunscreen does not protect the skin from all types of damage, so for maximum protection, it is recommended to cover up and seek shade during peak sun hours.
What do the numbers on the bottle mean?
The SPF number on a sunscreen bottle indicates how much UV radiation it lets through, not how much it blocks.
Sunscreen with SPF 15 lets through one-fifteenth of the sun’s rays, or about 7%. Thus, it filters out about 93% of UVB rays, while SPF 30 filters out about 97%.
The number of stars indicates the percentage of UVA absorption relative to the amount of UVB absorbed. The rating ranges from one to five stars, with five being the most effective.
A sunscreen with a low SPF can have a high rating because the ratio of UVA to UVB protection is the same as in products with a higher SPF.
The American Academy of Dermatology recommends choosing a product with an SPF of at least 30. The product should provide broad-spectrum protection against both UVA and UVB rays. Ideally, you need a sunscreen with a high SPF and a high rating. Apply it 15–30 minutes before going outside.
How effective is the best sunscreen?
All indicated levels of protection assume that the product is applied under ideal conditions. In reality, most people do not apply sunscreen perfectly, and it can wear off due to sweat or during swimming. Experts believe that most people apply only half of the recommended amount.
How much sunscreen should you apply?
AAD believes that one of the most important aspects of sun protection is how much product you need to apply. The formula depends on the type and consistency of the product.
- Creams and lotions should be applied in the amount of one ounce (28 g or a full shot glass) and then vary the amount depending on your proportions. It may seem like a lot, but that amount is just enough to cover all exposed areas of the body from head to toe.
- Sunscreen sprays are considered more convenient to apply than lotions. However, with sprays, you need to be more careful not to miss any areas. Spray each section for at least six seconds — about four seconds longer than we are used to.
- Stick SPF, often used for the face, is recommended to be applied at least twice — and don’t forget the ears and eyelids.
What About “Once-a-Day” Sunscreens?
There are many long-lasting products on the market that are advertised as once-a-day. Manufacturers claim they provide protection for up to eight hours if applied correctly.
However, dermatologists are quite critical of such products. In Which? report from 2016, these products were criticized for not living up to their claims. It was noted that after six to eight hours, the average level of protection decreased by 74%.
In general, AAD advises applying any sunscreen at least every two hours, even if it is cloudy outside. If you are swimming or sweating, you should apply it more frequently, such as every time you get out of the pool or ocean.
And, before going outside, make sure your sunscreen hasn’t expired, as most products last about two to three years.
