(CNN) -- Whether a person is light- or dark-skinned, whether it's cloudy or sunny outside, dermatologists recommend wearing sunscreen -- globs of it.
The simple act of enjoying the sun has become complicated with questions about how much sunscreen to use (more than you think), how often to apply (frequently) and what those acronyms (UVA, UPF, SPF) mean.
This week, the Environmental Working Group likened some sunscreens to "modern-day snake oil," calling most of the products ineffective and questioning their safety. It said that the products were "exposing people to potentially hazardous chemicals."
The report did not appear in a peer-reviewed scientific journal. Dermatologists say there is no evidence that sunscreen is unsafe and that going unprotected is much more dangerous.
The problem is that not all sunscreens are created equal, depending on their ingredients. And the scars of neglecting sun protection are chronicled on the iReport photo wall of pain.
The sun is not the only culprit. Frequent trips to tanning booths have been found to double or even triple risk of developing melanoma, the deadliest form of skin cancer, according to a study this week.
The rays from the booth or the sun can damage the skin cell's DNA, producing mutations that lead to cancer.
The National Council on Skin Cancer Prevention has declared the Friday before Memorial Day, which kicks off the summer, a "Don't Fry Day." Here are five tips to avoid joining iReporters' stories of their worst sunburns ever (ouch).
1. Clothing matters
All clothing protects the skin to some degree, said Dr. Ariel Ostad, a clinical assistant professor in the department of dermatology at New York University Medical Center.
A tightly woven fabric such as denim confers more protection than linen, because it allows less light penetration, according to the Skin Cancer Foundation.
While it's unlikely anyone would wear sunscreen underneath thin clothes, it might be worthwhile for extra sensitive people, Ostad said,
"Even with T-shirts, I see people who get burned," he said. "If someone has a history of cancer or is very fair skinned, it doesn't hurt to put it on," underneath the clothes.
Some companies create UV-absorbing clothes. These might be helpful for people who spend hours in the sun, because the fabric's weave is designed to protect against the sun, said Ostad, who has no relationship with any of the manufacturers.
These clothes have ultraviolet protection factor, also known as UPF, which indicates how much UV radiation can penetrate the fabric. A shirt with an UPF of 30 means just 1/30 of the sun's radiation can get through.
2. Sunscreens should have UVA and UVB protection.
UVB rays cause sunburns.
UVA rays age the skin, causing wrinkles and tans.
These are two types of ultraviolet radiation that damage and increases risks of skin cancer.
Make sure the sunscreen product has both UVB and UVA protection, dermatologists say. The key active ingredients to look for are zinc oxide and titanium dioxide, said Ostad.
"Evidence has shown the best sunscreens are the ones that block UVB and UVA," Ostad said. "The majority of these companies that market sunscreen products, they try to make people more aware of the SPF."
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3. A high SPF is hype.
The higher the Sun Protection Factor value, the better sun protection the product is supposed to provide against UVB light.
Research shows that an effective SPF 15 can block about 93 percent of all incoming UVB rays, SPF 30 blocks 97 percent and SPF 50 blocks 98 percent.
The protective factors plateau from there, Ostad said. A product with SPF 100+ blocks about 99.1 percent of the UVB rays.
"You don't really need a high number," Ostad said. "They end up being expensive and don't do more than SPF 50."
Keep in mind, SPF protects only against UVB rays. This fall, the U.S. Food and Drug Administration is expected to issue sunscreen labeling changes and a star-rating system to also measure UVA protection.
4. Sunscreen sprays are not as effective.
Sure, the sprays are easy to apply, but the downfall is they're less effective. Zinc oxide and titanium dioxide doesn't come in spray form. And most of the sprays protect mainly against UVB rays, Ostad said.
Another problem is that people don't use enough sunscreen, said Dr. Rutledge Forney, an educational spokesperson for The Skin Cancer Foundation.
An average person should use a dollop -- enough to fill a shot glass, she said. About one ounce of sunscreen should be applied 30 minutes before going outside and reapplied every two hours, she said.
"Whether the sun is out or not, put on sunscreen on your face and hands, just like you would brush your teeth twice a day," Forney said.
5. Darker skin tone isn't a free pass
Darker-skinned people have some natural protective qualities from their pigmentation, but it's no immunity against sunburn and skin cancer. African Americans, Hispanics, Asians and people of color get the disease, too.
It might be harder to diagnose skin cancer in these populations because the growths often appear in atypical locations such as palms, soles of the feet, toenails and fingernails.
Skin experts say all racial groups need to use sunscreens.
CNN's Sabriya Rice contributed to this report.