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Decoding SPF15 and Other Sunscreen Mysteries

It is next to impossible to walk out of the dermatologist’s office without being advised about sunscreen! Here are a few important facts about the most essential skincare product – your sunscreen.

Basics of SPF
Sun Protective Factor(SPF) is a laboratory measure of the time it takes for skin to burn when exposed to UVB. For instance, if you normally develop a sunburn in 10 minutes without wearing sunscreen, an SPF 15 sunscreen will protect you for 150 minutes (10 minutes multiplied by the SPF 15). A broad-spectrum ( protects against UVA and UVB rays), water-resistant sunscreen, with a SPF of at least 15 should be used year-round on exposed skin. For fair-skinned individuals with light-colored hair,  it is preferable to apply sunscreen with a higher SPF.

Physical Vs. Chemical Sunscreen
Sunscreens are of two types: physical and chemical. Physical sunscreens act by blocking the sun’s rays and are also referred to as sunblock. They contain titanium dioxide and zinc oxide and provide protection against UVA and UVB light. These are not aesthetically popular as they tend to leave a white film on the skin. The newer versions containing micronized particles have overcome this concern. Chemical sunscreens work by absorbing the Sun’s rays, and primarily filter UVB and only some UVA. Oxybenzone, avobenzone, sulisobenzone are some of the ingredients. Though avobenzone provides UVA blocking capability but tends to disintegrate upon exposure to light. Mexoryl, tinosorb, and octocrylene are photo-stabilizing, so you might want to look for these when buying a sunscreen

Sun, Snow, Clouds – Apply it all year round
Ultraviolet (UV) rays are the part of the light spectrum that reaches the Earth from the Sun. UVA is primarily responsible for the aging of the skin such as age spots and wrinkles. UVB causes sunburn and plays a major role in the development of skin cancer. UVA can penetrate glass windows so it is preferable to apply sunscreen even indoors to prevent your skin from photodamage. Sunscreen is not only for sunny days as 80 percent of Sun’s UV rays can pass through the clouds and cause unwanted effects. Sun’s reflective powers are great on snow as well as sand, so do apply while skiing and desert adventure trips. The rays are strongest between 10 am – 4 pm so it is ideal to avoid Sun during this period.

For Your Skin Type
The choice of the sunscreen varies according to skin type.

If you have dry skin: Opt for lotions and creams with hydrating components such as aloe and glycerin. Try to avoid alcohol-based products as they have a drying effect
In case of oily skin: Grease-less sunscreens work the best. Avoid mineral oil as a component.
For sensitive skin: Hypo-allergic, fragrance-free formulation will help you avoid the red blotchy skin.

If water sports and outdoor activity are your things: Prefer water-resistant or very water-resistant sunscreens. Water-resistant sunscreens maintain its SPF level after 40 minutes of water immersion whereas very water-resistant sunscreens maintain up to 80 minutes.

Along with the quality, the quantity is important too. Apply it liberally. One ounce is required to apply to the exposed parts of the body. For maximum benefit apply 15-30 minutes before going outdoors and reapply every two hours.

Dress It Up
Sunscreens are an important but not the sole form of Sun defense. It should be kept in mind that they provide limited barrier from UVA rays. Look out for sunglasses that are wraparound variety and provide UV protection. Broad-brimmed hats and clothing form an important part too. It is a well known fact that darker colors offer better protection than light colors but the most important factor is the tightness of the weave.SPF 30+ clothing are preferred.


Dr. Sidhu is a dermatologist with a special interest in procedural dermatology and is currently an International fellow at the department of dermatology, Harvard Medical School, Boston.

Photo by Retha Ferguson from Pexels

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