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Sun avoidance and regular sunscreen use are widely promoted by organizations and individuals interested in cancer prevention. However, 70% of those who participated in a beach survey were on the beach to get or to maintain a suntan. Although they stayed on the beach for an average of 4 hours, only half were using sunscreen.

On the mountains, and despite past sunburn experience, skiers often do not use sunblock. A springtime survey of skiers in Alberta showed that only two thirds were using sunscreen, and of those using a sunscreen, one third were sunburned at the time of survey.

There appears to be some confusion about the messages people are getting about sunscreens and why they’re so important. Some use sunscreens to prevent sunburn, whereas others use sunscreens to improve sun tanning. Some wish to avoid the wrinkling associated with sun exposure, and others believe that sunscreens prevent all types of skin cancer, yet others seem to believe that they can use sunscreens in order to prolong their time in the sun.

Why Use Sunscreens?

  • Prevents sun burns
  • Prevents photodamaged skin (aged look – brown spots, wrinkles)
  • Prevents actinic keratosis and perhaps squamous cell cancers
  • May prevent other skin cancers

What Is A Sunburn?

A sunburn is caused by exposing your skin to too much ultraviolet (UV) light from the sun, that is, lightwaves that measure approximately 200-400nm. UV light can be broken down into 4 component parts that include:

  • Ultraviolet A1 (UVA1), 340-400nm
  • Ultraviolet A2 (UVA2), 320-340nm
  • Ultraviolet B (UVB), 290-320nm
  • Ultraviolet C (UVC), 200-290nm

There are two major types of UV sun damage: UVA-type damage, with light wavelengths of 340-400nm, and UVC-type damage, which includes light wavelengths of up to 340nm. UVA-type damage can cause the skin to tan and may cause very weak burns, while UVC-type damage causes skin to burn.

How Much Sunscreen Should I Apply?

The average user of sunscreen tends to use significantly less sunscreen than the amount required to achieve the SPF listed on the container.

How Often Should I Apply Sunscreen When I’m Out In The Sun?

Many experts recommend that frequent application during sun exposure is required. However, a group of children were tested by spreading on one application of sunscreen to one side of their bodies, and four applications to the other.

They then spent 6 hours in the sun, one application provided the same level of protection as four applications, confirming the adequacy of a single daily application of a sunscreen in that situation.

How Long Before Sun Exposure Should I Apply Sunscreen To My Skin?

As molecules of sunscreen are present in their active state in the sunscreen, sunscreens work immediately upon application. The only reason for early application, is to allow absorption into the skin so that the sunscreen is less likely to be washed off, should the person be entering the water. Even so, modern sunscreens are quite resistant to removal from the skin.

Sun Protection Factor (SPF) – What Is It?

SPF is the ratio of the minimal ultraviolet dose required to produce redness with and without a sunscreen. For example, if it took ˝ hour for your skin to become sunburned without any sunscreen, then for a sunscreen that has a 15 SPF rating, you could stay in the sun for 15 times longer (or 7.5 hours) before you get sunburned. This is provided, of course, that you’ve applied the sunscreen properly so that you’re getting the prescribed protection.

Reactions To Sunscreens:

Sunscreens can be both an irritant and an allergen, though allergic reactions are rare. Irritant reactions, however, abound. One classic error in sunscreen application is to put a large amount of sunscreen on the forehead, perspiration and gravity can cause the sunscreen to migrate down your forehead into your eyes, causing a stinging sensation. Some people attribute this to an allergic reaction and discontinue use. It’s also important to wash your hands after applying sunscreen, since rubbing your sunscreen covered finger near your eyes can induce an irritant reaction.

Why Is It Important To Use Sunscreens During Childhood?

It appears that a great deal of time can elapse between actual sun damage and the development of skin cancer or other skin problems like photoaging therefore, it is important to protect your skin from an early age when you are out in the sun.

Sunscreens And The Elderly:

Many elderly people can become quite obsessed by sun avoidance, and their quality of life can suffer. Sometimes, if they are diagnosed with an actinic keratosis or basal cell carcinoma, they can become anxious and almost leap from shadow to shadow. However, few of them are likely to develop new skin cancers from present sun exposure. As long as they are prudent about avoiding excessive sun exposure, and protecting their skin to prevent sunburn, they can continue to enjoy time outdoors.

Can Sunscreens Prevent Cancer?

There is clear evidence that sunscreens are helpful in preventing actinic keratoses, which are warty lesions that can occur on sun exposed skin of the face or hands. Research has shown that these lesions can develop into a cancer called squamous cell carcinoma, and that this is linked to a cumulative exposure to the sun.

However, there is surprisingly little evidence that sunscreens have much effect in preventing another kind of skin cancer called basal cell carcinoma, or for malignant melanoma. For malignant melanoma and for basal cell carcinoma, the character and timing, that is, the type of sunlight and your age at the time of the exposure to the sun, appears to be more important than the cumulative dose.

Adapted from an article by David I. McLean, MD, and Richard Gallagher, MA.