What is SPF and why is it important?
SPF stands for Sun Protection Factor and is the universal measurement of protection against UV - ultra-violet - rays. It measures how much UV radiation is required to produce a sunburn on skin that's protected with sunscreen as opposed to how much UV radiation is required to produce a sunburn on unprotected skin.
Here's an example: An SPF 20 sunscreen will protect the skin against 20 times the exposure of UV rays than if you weren't wearing any sunscreen at all.
A common misconception is that a sunscreen's effectiveness can be calculated by multiplying the SPF value by the length of time it takes to get a sunburn without sunscreen. In reality, each person's sun exposure is dependent upon what time of the day it is, their geographic location, weather conditions, how long they're in the sun, and more.
The Importance of SPF
Studies have shown that the #1 cause of damage and aging to the skin is sun exposure. Excessive exposure to the sun's rays can cause wrinkling, a leathery skin appearance, and in worst cases - skin cancer. It's also been proven that overexposure to the sun can interfere with your immune system. Currently, sunscreen products containing a recommended SPF rating of 15 or above play an important role in helping diminish the harm of the sun's rays.
SPF Myths & Truths
With the increase in skin cancer diagnoses over the last decade, SPF has become a popular topic that you can find information about nearly everywhere. However, not all of it is true. Here are some of the most popular misconceptions - and facts - about SPF.
Myth: If I usually get sunburned in an hour, an SPF 10 sunscreen allows me to stay in the sun for ten hours (10 times longer) without getting burned.
Truth: SPF isn't directly related to how long you're exposed to solar radiation, but instead, the amount of solar radiation. Although these two things are related, there are many other factors that contribute as well. One of these is the intensity of solar energy.
You've probably heard that the sun is normally strongest mid-day, or between 10 a.m. and 4 p.m. That means that you could be exposed to the same amount of solar energy during one hour of outdoors time at 8 a.m., versus just 15 minutes at 1 p.m.
The amount of solar radiation you are exposed to can also be determined by where you live. Greater solar intensity occurs in cities at lower latitudes. Another factor is clouds - since they absorb solar energy, the intensity is usually greater on clear days.
Myth: Using SPF 60 sunscreen provides twice the sun protection of an SPF 30 sunscreen.
Truth: An SPF 30 sunscreen will protect against about 97 percent of UVB rays, and an SPF 60 or higher will protect against 99 percent of rays, which is only a slight increase in protection.
Myth: It's cloudy -- I don't need to wear sunscreen.
Truth: According to the FDA, up to 80 percent of the sun's UV rays can get through the clouds - even when it's overcast.
Myth: I found this old bottle of sunscreen in my medicine cabinet, but it's probably just as effective as a brand-new bottle.�
Truth: Sunscreens are designed to be effective and remain at their original strength for up to three years. Many even have an expiration date on the bottle that marks a time when the product will no longer be effective. You should throw away any sunscreen or tanning oil that's been in your cabinet for more than three years, or is past the expiration date.
Keep in mind, if you spend a lot of time outside and are applying your sunscreen properly, a bottle shouldn't last you that long. By following the guideline of a "shot glass" of sunscreen each time, a 16-ounce bottle will only last you 16 applications.
Myth: I'm going on vacation soon, and I heard it's better to get a "base tan" beforehand so I won't get sunburned.
Truth: A base tan does give your skin some protection, but the reality is that any change in skin color (whether before or during your trip) is due to your body's reaction to UV rays -- a sure sign that your skin is damaged. The more frequently your skin is exposed to UV rays, the more likely you are to experience premature skin aging and skin cancer.
Reprint from "The SPF Resource Guide", by Shelly Leonard