How to Use Sunscreen Correctly, According to a Dermatologist

Dr. Julia Carroll, co-founder of Compass Dermatology, explains how to use the product effectively to protect your skin from harmful agents.

Sunscreen is an indispensable part of daytime skincare, whether it’s a simple or an advanced routine. The product has various benefits, but the most common are protecting the skin from sunburn and maintaining a youthful look by slowing down the aging process.

Culture Magazin interviewed Dr. Carroll to understand the role of sunscreen in skin protection.

What are the adverse effects if we do not use sunscreen?

There is no such thing as a safe or healthy tan. A “base tan” provides little to no protection against sunburn, and any tan or change in skin color is a sign of skin damage.

Exposure to UVA and UVB radiation from the sun or tanning equipment can cause sunburn and eye damage, as well as increase the risk of skin cancer. Early exposure to tanning beds can increase a person’s chance of developing melanoma by up to 75 per cent and among those who first used a sunbed before age 35, the risk of melanoma is increased by 59 per cent.  

What do the SPF and PA numbers commonly found on product packaging mean?

SPF stands for Sun Protection Factor, and the number indicates how well the sunscreen protects skin against sunburn. One thing to know is that SPF numbers only give an indication of how well the sunscreen protects skin against UVB radiation, not the deeper-penetrating UVA. If you want protection against both, you’ll need to check that your sunscreen is ‘broad spectrum.’  Using a high-SPF sunscreen (SPF higher than 50) provides greater protection against sunburn and UV-induced skin cell damage over sunscreens with low SPF values. SPF 30 sunscreens block approximately 97 per cent of the sun’s rays. Higher number SPFs block slightly more of the sun’s rays but there isn’t a sunscreen that can block 100 per cent of the sun’s rays. It’s also important to remember that high-number SPF sunscreens last the same amount of time as low-number SPFs, and they all need to be reapplied throughout the day.

Some sunscreens include PA+ rating on their products. The letters “PA” followed by plus signs (PA+, PA++, PA+++, and PA++++) on a label are a rating system developed in Japan to represent how much UVA protection the product offers.

Is it true that we only need to use sunscreen when exposed to intense sunlight (such as in summer)?

People think that they can only be affected by the sun when they are in direct sunlight, but UV rays can get through clouds, fog and haze. Water, sand, concrete and especially snow can reflect, and even increase the effect of the sun’s rays. People should apply sunscreen every day when outdoors, driving in a car or indoors if they are working near a window. The sun emits harmful ultraviolet (UV) rays all year round, in fact, UVA rays remain constant in a location no matter what the season.

When do you apply sunscreen in a skincare routine to achieve the best effect? What about other cosmetic products that contain SPF? Should they be used as well? Or instead?

I apply my sunscreen first thing in the morning after my shower. This helps me to make sure I’ve got my full neck, shoulders and chest, as well as my face. Makeup typically won’t have enough SPF in it and it’s hard to tell if you have enough of it on for it to be effective. I recommend applying sunscreen before make-up.

Dr. Julia Carroll is a board-certified dermatologist and regular contributor to local and national media. Her philosophy is based on delivering realistic, natural results while bridging the gap between cutting edge and more established treatments. Dr. Carroll is the co-founder of Compass Dermatology in downtown Toronto.  She also holds a faculty position within the University of Toronto, Division of Dermatology.  Apart from her busy dermatology practice, she is the President of the Canadian Association of Aesthetic Medicine, the Ontario Director on the board of the Canadian Dermatology Association and a board member of Melanoma Network Canada.

What must we do after using sunscreen? For example, reapply after swimming? After sweating?

Health Canada recommends reapplying sunscreen every two hours, or after you sweat or swim. There is no such thing as waterproof sunscreen.  Sunscreens will be labelled water resistant 40 or 80 indicating that they are water resistant up to 40 or 80 minutes. Water-resistant sunscreen does not last all day. Even if your sunscreen is water-resistant, it should still be re-applied approximately every two hours when outdoors, even on cloudy or cold days, and after swimming or sweating.

What types of sunscreen are good for different skin types? Dry, oily and combination?

There are some sunscreens that can clog pores, but there are many options out there that won’t. If you have oily or acne-prone skin, keep an eye out for sunscreens labelled ‘non-comedogenic’ or ‘oil-free.’  If you have sensitive skin, I recommend my patients try using physical/mineral sunscreens. Many men prefer gel-based sunscreens and cream-based sunscreens are often preferred for those with a drier complexion. There truly is a sunscreen out there for everyone.[an1] 

Many people believe that using beauty products when they are too young could harm the skin. How does sunscreen affect the aging process of the skin? At what age should we start using sunscreen and how to use it correctly?

You’re never too young to begin protecting yourself from the sun. Sunlight consists of two types of harmful rays – UVA and UVB rays. UVA rays penetrate deep into the skin and can prematurely age your skin, causing wrinkles, age spots and worse, potentially skin cancer including melanoma. UVB rays are the primary cause of sunburn. While UVA and UVB rays differ in how they affect the skin, they both do harm. Unprotected exposure to UVA and UVB damages the DNA in skin cells, producing genetic defects, or mutations, that can lead to skin cancer. We recommend avoiding sun entirely before the age of six months and then after six months using sunscreen in addition to general sun smart behaviour.

Sometimes sweating causes sunscreen to run into the eyes, and it is painful and causes red, sore eyes. How can we prevent this?

I recommend that people who enjoy working out or running outside try using sunscreen sticks on their face. They are typically more waxy, and that helps to prevent having the sunscreen run into your eyes when you begin sweating.

Most of us are working from home right now due to the pandemic. Do we still need sunscreen at home? Will light from laptop/computer screens affect our skin?

There is some published data that blue light can be harmful to the skin.  While blue light can emanate from computer screens, by far the greatest source of bluelight is still the sun. You do need to be careful when working from home if you’re sitting beside a window all day. Glass reduces, but does not completely block, transmission of UV radiation, so you can still get sun damage through a window.

Do you have any other sunscreen tips to share?
  • Sunscreens should be broad-spectrum – this means that they will protect you from both UVA and UVB rays.
  • Look for sunscreens that are water-resistant.
  • Be sure to read the expiration date on the bottle. Sunscreen loses its effectiveness over time.
  • Look for a sunscreen that you feel comfortable with and are willing to apply every day.

The bottom line is that the best sunscreen is the one you’re willing to put on.

This post is also available in: Tiếng Việt

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