UV radiation from the sun is one of the most common — and most underestimated — health risks Canadians face every year. Too much exposure can lead to skin cancer, eye damage, and a weakened immune system. The good news is that simple, everyday steps can protect you and your family. This article explains exactly what UV radiation does to your body and how you can stay safe, whether you’re at the cottage, on a hiking trail, or just running errands on a bright summer day.
What Is UV Radiation?
Sunlight is a form of electromagnetic energy. It travels to Earth in invisible waves of different lengths. From a health standpoint, the most important parts of the sun’s energy are ultraviolet (UV) radiation, visible light, and infrared radiation.
UV radiation is invisible to the human eye. It is the part of sunlight most responsible for sunburns, skin aging, and skin cancer. Infrared radiation, also invisible, is what you feel as heat. Visible light is simply what lets us see the world around us.
According to Health Canada’s sun safety guidelines, UV radiation levels in Canada can be dangerously high — even on cloudy days or during winter months in southern regions.
How UV Radiation Affects Your Skin
Your skin is your body’s largest organ, and it takes the most direct hit from UV radiation. Long-term exposure causes real, lasting damage that goes far beyond a temporary sunburn.
Skin Cancer Risk
Prolonged UV exposure is the leading cause of skin cancer. There are two main types: non-melanoma skin cancers (which are more common but usually treatable) and melanoma (which is less common but far more dangerous). Worldwide, more than two million non-melanoma skin cancers and 200,000 malignant melanomas are diagnosed every year.
People with lighter skin have a higher risk because their skin produces less protective pigment. However, skin cancer can affect people of all skin tones. In addition, research shows that getting serious sunburns — especially during childhood — significantly raises your lifetime risk of melanoma.
The risk is also linked to recreational sun exposure and the use of tanning lamps or tanning beds. Health Canada strongly advises against the use of tanning beds for this reason.
Premature Skin Aging
UV radiation breaks down the fibres that keep your skin firm and elastic. Over time, this causes wrinkles, sagging, and a leathery texture. Dermatologists call this “photoaging.” It makes skin look significantly older than it actually is.
This kind of damage builds up slowly. Therefore, even moderate daily sun exposure without protection adds up over the years. Wearing sunscreen every day — not just at the beach — makes a real difference.
How UV Radiation Affects Your Eyes
Many Canadians protect their skin but forget about their eyes. UV radiation causes serious eye damage, both in the short term and over a lifetime of exposure.
Short-Term Eye Damage
Acute UV exposure can cause photokeratitis and photoconjunctivitis. Think of these as sunburns on your cornea and eyelids. They are painful and uncomfortable. However, the good news is they are reversible and easy to prevent by wearing proper UV-filtering sunglasses.
Long-Term Eye Damage
Chronic UV exposure is much more serious. It can lead to cataracts, which cloud the lens of the eye and cause vision loss. The World Health Organization (WHO) estimates that more than 20% of the approximately 20 million people worldwide who are blind due to cataracts developed the condition as a direct result of UV radiation.
Furthermore, UV exposure can cause pterygium — a non-cancerous but uncomfortable growth on the surface of the eye — as well as squamous cell cancer of the conjunctiva.
Staring directly at the sun or other intensely bright objects can also damage the fovea, the most sensitive part of the retina. When these cells are destroyed, a person loses the ability to see fine detail. This makes it impossible to read, drive, recognize faces, or watch television. It is a serious and often permanent disability.
How UV Radiation Affects Your Immune System
This is perhaps the least well-known effect of UV radiation — and one of the most important. Research suggests that UV exposure can suppress your immune system by changing how immune cells behave and where they are distributed in the body.
Studies in both animals and humans show that UV radiation reduces the body’s ability to fight off certain infections. It may also reduce how well vaccines work in some people. As a result, people who spend a lot of time in the sun without protection may find their immune defences are weaker than expected.
Researchers are still studying this area. However, the early evidence is strong enough that public health experts take it seriously. This is one more reason why sun protection matters beyond just preventing sunburn.
Heat and Infrared Radiation
Infrared radiation — the part of sunlight you feel as warmth — also carries health risks at high levels of exposure. Excessive heat can cause heat stroke, heat exhaustion, and other dangerous heat-related illnesses.
Older adults, young children, and people living with disabilities are especially vulnerable. During Canadian heat waves — which are becoming more frequent due to climate change — these groups face the greatest risk. At moderate levels, though, the warmth of the sun is pleasant and relaxing.
If you or someone you care for belongs to a high-risk group, make sure to stay cool, stay hydrated, and limit time outdoors during the hottest parts of the day.
How to Protect Yourself from UV Radiation
The great news is that UV radiation damage is largely preventable. A few smart habits can protect your skin, your eyes, and your immune system all at once.
Clothing and Hats
Covering up is the single most effective form of sun protection. Wear long sleeves, long pants, and a wide-brimmed hat whenever possible. Tightly woven, darker fabrics offer the best protection. Some clothing is even rated with a UPF (Ultraviolet Protection Factor) label, similar to SPF in sunscreen.
Sunscreen
Use a broad-spectrum sunscreen with an SPF of 30 or higher on all exposed skin. “Broad-spectrum” means it blocks both UVA and UVB rays. Apply it generously and reapply every two hours, or more often if you are swimming or sweating.
An important note: sunscreen should not be used as an excuse to stay in the sun longer. It is a backup layer of protection, not a licence to bake. Use it alongside shade and clothing, not instead of them.
Sunglasses
Choose sunglasses that block 99–100% of both UVA and UVB radiation. Wraparound styles offer the best coverage. Polarised lenses reduce glare but do not automatically block UV — always check the label.
Timing Matters
UV radiation levels are highest between 11 a.m. and 3 p.m. Try to plan outdoor activities before or after this window. Seek shade whenever you can, especially during peak hours. Canada uses the UV Index to measure daily radiation levels — you can check it in the weather forecast on the Environment and Climate Change Canada website.
When to See a Doctor
You should speak with your family doctor or visit a walk-in clinic if you notice any of the following:
A mole or skin spot that has changed in size, shape, or colour
A sore on your skin that does not heal after several weeks
Unusual redness, swelling, or pain in your eyes after sun exposure
Blurred or cloudy vision that is getting worse over time
Any skin growth that looks different from others on your body
Most provincial health plans in Canada cover skin examinations by a family doctor. If your family doctor spots anything concerning, they can refer you to a dermatologist or ophthalmologist. Early detection of skin cancer or cataracts leads to much better outcomes — so do not wait.
If you do not have a family doctor, a walk-in clinic can assess skin changes and refer you as needed. Your health is worth the trip.
Frequently Asked Questions About UV Radiation
What does UV radiation do to your skin?
UV radiation damages the DNA in your skin cells, which can lead to sunburn, premature aging, and skin cancer over time. Long-term exposure breaks down the fibres that keep skin firm, causing wrinkles and sagging. Protecting your skin from UV radiation every day — not just on sunny days — is the best way to reduce these effects.
Can you get UV radiation damage on a cloudy day in Canada?
Yes — up to 80% of UV radiation passes through clouds, so overcast skies do not offer full protection. Snow and water also reflect UV rays, which can increase your exposure significantly. Health Canada recommends checking the UV Index daily and applying sunscreen whenever the index is 3 or higher.
What SPF sunscreen should I use to protect against UV radiation?
Health Canada recommends using a broad-spectrum sunscreen with an SPF of at least 30 to protect against UV radiation. Apply it generously to all exposed skin 15 to 20 minutes before going outside. Reapply every two hours, or right after swimming or sweating heavily.
Can UV radiation damage your eyes?
Yes, UV radiation is a leading cause of cataracts and other serious eye conditions. It can also cause painful short-term conditions like photokeratitis, which is essentially a sunburn on the surface of the eye. Wearing sunglasses that block 100% of UVA and UVB rays is the most effective way to protect your eyes.
Does UV radiation affect the immune system?
Research suggests that UV radiation can suppress the immune system by altering the behaviour of immune cells in the skin and body. This may increase your vulnerability to certain infections and could reduce the effectiveness of some vaccines. Scientists are still studying this area, but it is another strong reason to practise sun safety.
What time of day is UV radiation the strongest in Canada?
UV radiation is strongest between 11 a.m. and 3 p.m., regardless of the season or your location in Canada. During these hours, you should seek shade, wear protective clothing, and apply sunscreen. You can check the daily UV Index through Environment and Climate Change Canada’s weather forecast tools.
Key Takeaways
UV radiation from the sun causes skin cancer, eye damage, and immune system changes — all of which are largely preventable.
Skin cancer risk is highest in people with lighter skin, but affects all Canadians. Childhood sunburns significantly raise your lifetime risk.
UV radiation is a leading cause of cataracts worldwide. Sunglasses with full UV protection are essential, not optional.
UV rays reach you even on cloudy days. Check Canada’s daily UV Index and protect yourself whenever it hits 3 or above.
Use broad-spectrum SPF 30+ sunscreen, wear a hat, cover up, and avoid peak sun hours between 11 a.m. and 3 p.m.
See your family doctor or visit a walk-in clinic if you notice any unusual skin changes or worsening vision. Early detection saves lives.
Always speak with your doctor before making significant changes to your sun care routine, especially if you have a personal or family history of skin cancer.
