Protection Against the Sun: Which SPF to Use

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The acronym “SPF” on sun protection creams is short for Sun Protection Factor. SPF ratings start at two and can reach as high as 70. The sun protection factor in sunscreens indicates the product’s level of protection from UVB sun rays (how much UVB it’s blocking out), as well as the duration of protection.

Although the SPF ranking system is based on the level of UVB protection, some sunscreens also provide protection from UVA. These products are referred to as “full spectrum” or “broad spectrum” and contain the UVA protection symbol. According to regulation, these products have to provide a minimum level of UVA protection with a ratio of 1:3 for UVA: UVB protection.

Although most people understand the importance of wearing SPF, not many know which level of SPF protection to use or how to choose the right sunscreen for their skin type. To answer this question, let’s first look at how SPF works.

What Does the SPF Number Mean?

The SPF number is an indication of the amount of time the lotion will protect skin against the sun when using the product as directed. The duration of protection is calculated by multiplying the sun protection factor (SPF) with skin’s natural protection in minutes.

For example, a person with fair, sensitive skin that is extremely prone to sunburn will typically have about 10 minutes of natural protection before sunburn and UV damage set in. Therefore, if the person applies SPF 30 it would provide approximately 300 minutes of protection against the sun.

This is a fairly simple explanation of what the SPF number means, but it still does not touch on how to choose the right protection factor for your skin type. Knowing which SPF to use does not only depend on the duration you will be out in the sun. Other factors that should be considered in determining the optimal SPF for your skin, are skin sensitivity to sun (skin pigmentation) and radiation intensity. That’s why it’s so important to know when the sun’s rays are most potent. This will help you apply an appropriate level of UV protection.

Understanding UV Intensity

According to the United States Environmental Protection Agency (EPA), an easy way to determine how much UV rays you are being exposed to, is by looking at your shadow. If your shadow is taller than you are (like early morning and late afternoon) your UV exposure is likely to be lower. If your shadow is shorter than you are, around noon, you should be extra careful because this is the time of day you are being exposed to higher levels of UV radiation.

Another, more accurate, way of determining the sun’s potency on any given day is referring to the Ultraviolet (UV) Index in your area each day.

What is the UV Index? The UV Index provides a daily forecast, calculated by the National Weather Service, of the expected risk of overexposure to UV radiation from the sun. The UV intensity level is predicated on a 1-11+ scale to indicate the level of risk for the average person from unprotected sun exposure. The meaning of each UV Index category is as follows:

• UV Index 0-2 – low danger
• UV Index 3-5 – moderate risk
• UV Index 6-7 – high risk
• UV Index 8-10 – very high risk, extra precautions needed
• UV Index 11+ – extreme risk, take all precautions, unprotected skin and eyes can burn in minutes

The UV Index is a great tool to use before going outside. The higher the UV Index rating, the higher the SPF should be.

How to Choose the Right SPF

So which SPF should you apply? As mentioned before, the correct SPF depends on your skin’s sensitivity to sun rays, and the UV Index rating for the day.

For example, on a day with a low UV index rating of 0-2, a person with fair, extremely sensitive skin will be sufficiently protected from the sun by applying SPF 20-30, while a person with less sensitive, dark skin will only need an SPF 15. On days with moderate to high UV index ratings, sensitive skin will need SPF 50+ whereas less sensitive skin will have sufficient UV protection with an SPF 20-30. On days with very high UV exposure, an SPF 50+ is recommended for all skin types.

Does High SPF Protect the Skin Better?

SPF measures a sunscreen’s effect against UVB sun rays and the amount of time an individual can be in the sun before burning.

So, does a higher SPF protect skin better?

Under ideal conditions, yes.

A sunscreen with higher SPF protection and broad-spectrum coverage (protecting skin from UVA and UVB) is more effective in shielding skin against sunburn, UV damage and DNA damage than lower SPF products.

• SPF 15 blocks 93% of UVB rays
• SPF 30 blocks 97% of UVB rays
• SPF 50 blocks 98% of UVB rays

However, in real life, sunscreen lotions with a very high SPF often create a false sense of security, which means that people who use them tend to stay out in the sun for much longer without seeking shade, wearing a hat or covering up with clothing. This results in a lot more UV damage, which, of course, defeats the purpose. Many of these people may also skip reapplying sunscreen.

It’s important to note that regardless of the SPF, sunscreen lotions need to be reapplied every two hours (or immediately after swimming or sweating). And because sun protection creams take some time bond to the skin, they should be applied 30 minutes before going outside.

Taking good care of your skin means wearing sunscreen every day. This will not only decrease your risk of developing skin cancer but will also delay the aging process.