Summer is the time of year when we all head outside and enjoy long days, warm weather and a plethora of activities.

Since we’re outside so much, we’re also susceptible to sunburns. The best way to avoid sunburn and still go outside is to use sunscreen. Here’s what you need to know about sunburn and sunscreen.

What is a sunburn?

A sunburn is inflamed, painful skin that is hot to the touch and appears after a person has been in the sun too long, according to the Mayo Clinic. It happens because of prolonged exposure to ultraviolet light from the sun. The UV light damages skin cells and the immune system increases blood flow to the area which causes inflamed skin.

Intense, repeated sun exposure, even without sunburn, increases your risk of skin cancer, such as melanoma. It can damage the DNA of skin cells. Sunburns in childhood and adolescence may increase the risk of melanoma later in life.

How to avoid sunburn

• Avoid sun exposure between 10 a.m. and 4 p.m.: The sun’s rays are strongest during these hours so it’s best to remain indoors.

• Use sunscreen often and generously: Use water-resistant, broad-spectrum lip balm and sunscreen even on cloudy days

• Cover up. Use items such as umbrellas or wide-brimmed hats can offer protection in addition to sunscreen. Dark clothing with a tight weave offers more protection. Consider using outdoor gear specially designed to provide sun protection.

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What kind of sunscreen should I use?

When going outside, you should apply sunscreen with a sun protection factor or SPF of at least 30, according to the Mayo Clinic. You should apply it 30 minutes before going outside and reapply every two hours — more often if you are swimming or perspiring.

What does SPF mean?

SPF is how much solar energy is required to produce a sunburn on protected skin relative to the amount of solar energy required to produce sunburn on unprotected skin, according to the Food and Drug Administration. As the SPF value increases, the solar protection increases.

Which SPF is best?

The American Academy of Dermatology recommends using a sunscreen with an SPF of at least 30, which will block 97% of the sun’s UV rays. A high SPF number will block slightly more of the sun’s UV rays, but no sunscreen can block 100% of the rays.

How long does SPF 50 last?

A higher SPF number does not mean you can spend a longer amount of time in the sun without reapplication. It means it will block more UV rays, but the difference between SPF 30 and SPF 50 is slight.

However, according to the American Academy of Dermatology, many individuals only apply about 20% to 50% of the amount of sunscreen needed to achieve the amount of SPF on the label so the application of high-SPF sunscreens helps to compensate for this under-application.

How to treat a sunburn

If you do get a sunburn, the American Academy of Dermatologists recommends the following to treat it:

• Take frequent cool baths or showers to help relieve the pain.

• Apply a moisturizer that contains aloe vera or soy.

• Take aspirin or ibuprofen to help reduce any swelling and discomfort.

• Drink extra water.

• If your skin blisters, allow the blisters to heal. Do not pop the blisters, as blisters protect you from infection. Keep blisters clean and apply petroleum jelly to protect them while they heal.

This article originally appeared on Delaware News Journal: What is SPF? How to avoid sunburns, pick a sunscreen