Photo-protection is a key preventative health strategy based on evidence that sunscreens can help to reduce the risk of skin cancers and other skin damage. Avoiding the sun completely is unrealistic for most people, so the regular use of a sunscreen is a useful compromise. Sun exposure is a factor in the development of three types of skin cancers. Basal cell carcinoma, the most common skin cancer, is caused by the exposure to ultraviolet (UV) radiation. It affects fair-skinned individuals with blond or red hair who often burn with sun exposure. Squamous cell carcinoma, the second most common form of skin cancer, is caused by chronic sun over-exposure and is highly treatable when identified early. Malignant melanoma is a less common skin cancer for which sun exposure is the main environmental factor. If found early, the disease has a 90% cure rate; however, if left unattended, it eventually reaches the blood stream or lymphatic system and can lead to death. Used appropriately, sunscreen has been shown to reduce the incidence of skin cancer. Sunscreen products that offer better protection against UVA rays may help prevent drug-induced photosensitization and light-induced or light-aggravated skin conditions.


Ultraviolet Radiation

Ultraviolet rays are responsible for skin damage, wrinkling, premature aging and skin cancer. There are three categories of ultraviolet rays based on the length of the rays. UVA (long wavelength) light is not as powerful as UVB light, however these rays penetrate deeper into the skin. UVB (medium length) rays are more intense during the summer months, primarily affecting the outer layers of the skin. UVB light is the primary cause of sunburn, skin aging and skin cancer. UVC (short wavelength) are the strongest, most dangerous rays; however, they are typically filtered out by the ozone layer before reaching the surface of the earth.


Sun protection factor (SPF)

A “broad spectrum” sunscreen provides protection through the entire spectrum of both UVA and UVB. A “water-resistant” product maintains the SPF level after 40 to 80 minutes of water immersion.

As illustrated below, beyond the basic SPF15, higher SPF products seem to provide minimally stronger UVB protection.

SPF 15 = 93% of UVB rays filtered

SPF 30 = 96.7% of UVB rays filtered

SPF 50 = 98% of UVB rays filtered

Technique is the Success to Sunscreen Protection!

More important than a sunscreen’s SPF, however, is its application. In outdoor tests of SPF, the effectiveness of the products is found to be lower than in the laboratory, which is likely attributable to application factors. In outdoor comparisons of SPF15 and SPF30 sunscreens, SPF 30 sunscreens have shown to provide significantly greater UVA and UVB protection. Note that while an SPF of higher than 50 does provide greater protection, the exact amount is controversial. In Canada, sunscreens with SPF of up to 60 are available.

It is important that sunscreen users apply the proper kind of sunscreen and one that provides a broad protection from both UVA and UVB rays. Also, individuals do not use nearly enough sunscreen – the correct dosage is approximately a shot glass of sunscreen to be initially applied approximately half an hour before going outdoors. To be properly protected, two to three teaspoonfuls should be applied to each arm and three to four teaspoonfuls per leg. In addition, the product must be reapplied every few hours, especially when swimming, riding, running or playing other sports.

The following are some important tips on the use of sunscreen products:

  • Look for the CDA (Canadian Dermatology Association logo) on sunscreens

  • Use a broad-based sunscreen with UVA and UVB protection, with a minimum sun protection factor (SPF) of 30

  • Apply the proper amount of sunscreen half an hour before going out into the sun and reapply regularly throughout the day – even more frequently if you are exercising in the heat

  • Reduce exposure to the sun’s rays at their peak, particularly between 11:00 a.m. and 4:00 p.m.

  • When taking antibiotics or acne medication it is important to be especially cautious about exposure to the sun owing to an increased risk of photosensitization with these drugs- when in doubt ask your pharmacist!

  • For the best UVA and UVB protection wear a broad-brimmed hat and wrap-around sunglasses

  • Wear clothing that covers and protects as much as possible

  • Look for shaded areas during outdoor activities

  • Even when using self-tanning creams, it is important to apply sunscreen as recommended. The darker skin from self-tanning creams does not provide protection from the sun

  • Check the daily local forecast for “UV ratings” and cover up accordingly.

If you have any questions regarding sunscreens or medication(s) that may make you more sun-sensitive ask your Smith Drugs and Apothecary pharmacist!


Norm Corriveau, B.Sc.Phm.


Drugstore Canada ,“Summer Skincare”, June 2012

Drugstore Canada , “ 2012 Skin Health”, May 2012

Self-Medication, Canadian Pharmacist Association 6th edition

Compendium of Nonprescription Products, Canadian Pharmacist Association, 2011