Sunscreens protect the skin against sun damage. However, you may still be vulnerable to the harmful ultraviolet radiation of sunlight in spite using sunscreens religiously. This may be because you may be using the wrong SPF!

What is SPF?
SPF is the Sun Protection Factor that tells you about how long a person can stay protected from the UVB rays of the sun. For example, if a person can stay in the sunlight for 15 minutes without getting burnt, an SPF 30 sunscreen can increase the time thirty times over, i.e. if originally a person can sustain sunlight for 15 minutes, by applying a sunscreen with SPF 30, he/she can stay in the sun for 15 x 30 = 450 minutes (7 and a half hours)

Generally, SPF 15 suffices most people and allows them to be out in the sun for about 2 ½ hours before experiencing signs like skin redness. However, an ironical fact is SPF 15 protects against 93 percent of UVB radiation, whereas SPF 30 defends against 97 percent of the same.

Ultraviolet Radiations of the Sun

The sun's ultraviolet spectrum is comprised of three main types of rays – UVA, UVB and UVC.

UVA Rays – These rays penetrate deep inside the skin and cause intrinsic damage which further leads to premature aging with appearance of wrinkles, fine lines and age spots. There is no immediate signs of damage like sun burn but the skin deteriorates gradually. Research also suggests that UVA rays cause cataract and blindness. Moreover, it aggravates the damage caused by UVB rays and promotes development of skin cancer.

UVB Rays – These are powerful rays responsible for causing sunburn. In addition, they also cause squamous cell and basal carcinomas and melanoma.

UVC Rays – These rays are the most harmful of all but fortunately, they get absorbed by the ozone layer of the atmosphere.

What SPF Do You Need?
Generally, an SPF 15 is enough if you are indoors most of the time and just need to avoid incidental exposure. But if you need to spend a longer time outside in the sun, you should use a sunscreen with SPF 30 or more. People with fair skin and those who have extra sensitive skin should choose to use a sunscreen with SPF 50 that guarantees 99 percent protection

Tips to Use Sunscreens Effectively
Use a sunscreen that offers broad spectrum protection against both the UVA as well as the UVB rays of the sun. The sunscreen should contain ingredients like avobenzone, titanium dioxide or zinc oxide.

Even 'waterproof' and 'water-resistant' sunscreens don't offer protection all day long. Water-resistant sunscreens are usually effective for about 40 minutes after you swim or get wet and Waterproof sunscreens are effective for about 80 minutes. In both cases, you need to reapply the sunscreens after contact with water. Waterproof and water resistant sunscreens are especially useful if you engage in physical activities that make you sweat like exercising, running, jogging, etc.

Take out about an ounce of sunscreen in your palm and slather it on to all the exposed parts of your body including your ears, neck, shoulders, chest, back, hands and feet. Apply an SPF lip balm on your lips as well.

Apply sunscreen about 15 to 20 minutes before you venture out in the sunlight. This gives the sunscreen ample time to get absorbed into the skin and protect against sun damage. Make sure you reapply throughout the day.

Use a sunscreen that suits your skin type. People with oily skin should use a lightweight oil-free sunscreen, preferably serums or gels so that it doesn't increase the greasiness of the skin. Likewise, people with dry skin should opt for a heavy moisturizing sunscreen cream or lotion that apart from offering sun protection, hydrates the skin as well.

Don't use the sunscreen after its expiration date. If the expiration date is not specified, throw it away after about an year.

Make sure the sunscreen container is tightly sealed after use and store it in a cool, dry place in order to increase its shelf life.