With the weather finally warming up and tempting people to get outside, a dermatologist is sharing a reminder to protect our skin from serious damage when we spend time in the sun.  

The effects of a sunburn, while immediately painful, also have a long-lasting sting, says Hermenio Lima, a dermatologist and associate clinical professor with the Department of Medicine in the Faculty of Health Sciences.

Cases of melanoma and other skin cancers are rising, especially among young people, according to the Canadian Dermatology Association. 

“When you get a sunburn, you kill the keratinocytes, the primary cell that makes up the outer part of the skin,” Lima says.

“Melanocytes, the cell that produces your pigment, survive. And if the burn is bad enough, it can cause a mutation that forms melanoma. Other skin cancers can also form due to sunburns, but might manifest 20-30 years from now.” 

We spoke with Lima about sun safety, what sunscreen to use and common misconceptions that circulate online.  

What is the UV Index and how can it be used to understand sun dangers? 

The first thing I teach people is about ultraviolet (UV) rays and the UV Index, a scale that measures the intensity of the sun’s rays. The index, which was created by a Canadian, ranges from zero to 11+. The higher the number the more intense the rays. 

By consulting the UV Index on any given day, you can better prepare and protect yourself. Most weather apps and websites provide a UV forecast. 

It’s a very important component that many people don’t know. 

There are many different types of sunscreens available. What should people look for? 

There are basically two types of sunscreens, the mineral and the chemical sun blocks. Both are effective in sun protection, but I recommend people use mineral sunscreen instead of chemical sunscreen because chemical sunscreens tend to cause more allergies. Mineral sunscreen is mainly made from particles of zinc oxide and titanium dioxide. Because of this, there is much less interaction with the skin. 

Chemical sunscreens can interact with proteins in our skin and generate what we call a new antigen. That new antigen can be seen by our immune system as a different protein and can develop antibodies to deal with it.

For this reason, it’s very common for people to experience worsened eczema. Also, the mineral sunscreen should be used by children because it does not contain chemical substances that can sensitize the immune system to them. 

SPF is a term that gets thrown around a lot in sunscreen conversations. What does it mean and what should people be looking for? 

SPF stands for Sun Protection Factor. It is a measure of how well a sunscreen protects against UV rays. Imagine this: Photons are tiny packets of light energy — the smallest building blocks of sunlight. Some of them carry ultraviolet (UV) radiation that can damage your skin.

Sunscreen acts like a protective mesh that filters out most of these UV photons. For example, SPF 30 lets only 1 out of every 30 UV photons through, while SPF 50 allows only 1 out of 50. So, the higher the SPF, the tighter the mesh, and the fewer harmful photons can reach your skin.   

No sunscreen is going to cause complete blockage of the sun. It is just a ratio. So, the higher you go, the fewer photons will pass to your skin. The minimum recommendation is SPF 30.  

It’s important to remember that about 15 minutes after applying sunscreen is when you’re most protected. After that point, the SPF will gradually decrease. 

There are many claims online about sunscreen causing cancer. Is there any truth to this? 

Simply put, no. Sunscreen has been proven many times over to be safe. When used correctly, it protects the skin against harmful UV rays, which are a major cause of skin cancer. 

Some people talk up the benefits of homemade sunscreen. How safe is it? 

People may be drawn into making their own sunscreen for several reasons. It could be cost. It could be because they believe it’s safer. But there is no way for the average person to know how to measure SPF or its duration.  

When we are talking about a homemade kind of sunscreen, I have no insight into usage or how safe it is. It’s not a product that is tested and proven beneficial.

If someone comes to me and says, “I prepare my own sunscreen at home,” I tell them, “I cannot advise you to do that because the capacity of the sunscreen is unknown.”

Does sunscreen impact our ability to synthesize vitamin D from the sun? 

A myth we see, especially among elderly people because of osteoporosis, is that using sunscreen will prevent the body from synthesizing vitamin D.  That’s not the case; vitamin D production still occurs because, as we said before, no sunscreen blocks completely the light from reaching the skin. 

Nowadays you do not need to worry about lack of vitamin D as much because we add it in milk, orange juice, and many other things. 

Aside from sunscreen, are there other steps people can take to protect themselves from the sun? 

Yes. In fact, wearing the proper clothes can make a big difference. There are clothes specifically designed to protect against UV rays. These are often made with very breathable fabrics. 

Generally, fabric used in common clothes is about SPF 5-10. Remember, with sunscreen we recommend SPF 30 as a minimum. I always say if you hold the fabric up to the sky, if you are able to see the sun peeking through, that means those rays are going to pass to your skin.