Sun Rays

There are two types of UV rays that reach the earth and cause damage to the skin: UVA (320-400 nm) and UVB (290-320 nm) rays [2].

UVA rays penetrate the deepest skin layers and cause premature skin aging. They may also contribute to skin photoallergies, affect immune system functions, and are responsible for the development of some skin tumors.

UVB rays mainly penetrate the upper skin layers and are responsible for skin erythema (burning). UVB rays play a major role in the development of skin cancer [2-5].

Protection from Harmful UV Rays

A few simple action steps can make all the difference in protecting your family from the  harmful effects of UV rays. 

Apply Sunscreen

Apply generously broad-spectrum sunscreen with an SPF number of 30 to 50+ [6,7] on all skin surfaces not covered by clothing. 

Use Caution near Reflective Surfaces

Water, snow and sand reflect sunlight increasing the exposure to damaging UV rays.

Wear Protective Clothing

Wear protective clothing, such as a long-sleeved shirt, sunglasses, and a wide-brimmed hat.

Protect your Children

Children need to be even more protected as their skin and eyes are more sensitive to UV rays. Newborns should never be exposed to the sun.

Seek Shade

Always seek shade and avoid sun exposure between 10am and 2pm, when the sun’s UV rays are strongest.

5 Action Steps

Your Sunscreen

Use sunscreen with a Sun Protection Factor (SPF) number of 30 to 50+ [6,7] (for extreme conditions) on all skin surfaces not covered by clothing . 

SPF indicates the level of protection against UVB rays, not against UVA rays. The SPF number is obtained by measuring the amount of UV radiation dose needed to redden sunscreen-protected skin compared to unprotected skin [8]. 


An SPF 15 blocks approximately 93% of UVB rays while an SPF 30 filters out approximately 97% of UVB rays. An SPF 50 blocks about 98% of UVB rays. Beware of some higher SPF sunscreens since no sunscreen blocks completely all UV rays [9].

Make sure to always use a broad-spectrum (UVA+UVB) sunscreen. Protection against UVA rays is paramount since they result in deeper skin damage or other health problems. Sunscreens that offer UVA+UVB protection are tested in vivo by an independent laboratory according to an FDA standard test that assesses their broad-spectrum effectiveness.

Sunscreen should be applied liberally and evenly. Always make sure to carefully read the instructions on the label of your sunscreen for appropriate use.


5 Action Steps for Optimal Sun Protection

We all enjoy some exposure to sunlight but overexposure to ultraviolet (UV) radiation from the sun can be dangerous. Excessive UV exposure can result in sunburns or more serious health problems such as skin cancer, the most common form of cancer in North-America [1].


Elizabeth Hartinger, Ph.D., M.A.Sc., B.Eng.


[1] Canadian Skin Cancer Foundation. About Skin Cancer. Retrieved from:

[2] Mancuso JB, Maruthi R, Wang SQ, Lim HW. Sunscreens: An Update. Am J Clin Dermatol. 2017 Oct;18(5):643-650.

[3] van der Pols JC1, Williams GM, Pandeya N, Logan V, Green AC. Prolonged Prevention of Squamous Cell Carcinoma of the Skin by Regular Sunscreen Use. Cancer Epidemiol Biomarkers Prev. 2006 Dec;15(12):2546-8.


[4] Green AC, Williams GM, Logan V, Strutton GM. Reduced Melanoma After Regular Sunscreen Use: Randomized Trial Follow-Up. J Clin Oncol. 2011 Jan 20;29(3):257-63.

[5] Seité S1, Fourtanier AM. The benefit of Daily Photoprotection. J Am Acad Dermatol. 2008 May;58(5 Suppl 2):S160-6.

[6] Health Canada. Sunscreen Monograph. Retrieved from:

[7] Herzinger T. Sun Protection Factor 50+ : Pro and Contra. Hautarzt. 2017 May;68(5):368-370.

[8] Skin Cancer Foundation. Sun Protection. Retrieved from:

[9] Schalka S, Reis VM. Sun Protection Factor: Meaning and Controversies. Br J Dermatol. 2015 Nov;173(5):1345.

Information contained in this website is not intended nor implied to be a substitute for professional medical advice, it is provided for educational purposes only. You assume full responsibility for how you choose to use this information.Always seek the advice of your physician or other qualified healthcare provider about any questions you may have regarding a medical condition or treatment.

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