The Food and Drug Administration's new sunscreen regulations will require lotions to protect against both UVA and UVB rays, and will not allow them to be marketed as waterproof, only water-resistant. A proposed rule up for public comment would also ban labeling sunscreen with SPFs higher than 50.

Dr. Joseph Sobanko, a dermatologic surgeon at the Hospital at the University of Pennsylvania, said lotions with SPFs of 80 or 90 are just not more effective. Think of the sun protection curve as an asymptote, he said.

"When you're applying an SPF of 15, you're blocking out about 92 and a half percent of radiation from the sun,” Sobanko said. “When you approach an SPF of 20, you're blocking about 95 percent of UV rays."

At SPF 40, that only bumps up to 97.5 percent.

"A double in the SPF does not translate into a double of the amount of ultraviolet rays that you're blocking out,” Sobanko said.

Higher numbers don't seem to add much protection, but do bring additional risks, Reynold Tan, with the FDA’s Office of Nonprescription Products.

"With higher SPF products what manufacturers are typically doing is increasing the number of active ingredients or increasing the concentration of active ingredients in those products,” Tan said. “With increasing numbers of active ingredients you increase the risk of skin irritation or skin sensitization."

Some manufacturers, including Johnson & Johnson, disagree, and say they have submitted data showing higher SPF lotions do provide more protection from the sun. The public comment period will last 90 days, and the FDA said if convincing evidence is presented the rule will be changed.

Instead of reaching for a higher SPF and gaining a false sense of security when out in the sun, Penn's Sobanko said fair-skinned sun lovers should apply enough sunscreen.  He says it takes about a shot glass-full to cover an adult body.  You should also re-apply every 90 minutes, and cover up with wide-brimmed hats and long-sleeved shirts for maximum protection.