According to a study conducted by the Center for Drug Evaluation and Research, it took just one day of use for common sunscreen ingredients to enter the bloodstream at high levels. The study was published on Monday in the medical journal JAMA. It showed in the study that the blood concentration of three of the ingredients continued to rise as the daily use of sunscreen was continued, and it remained in the body 24 hours after the sunscreen use.

The four chemicals that they studied are avobenzone, oxybenzone, ecamsule, and octocrylene. These four are just a part of a dozen that the FDA recently said needed to be researched by manufacturers before they could be considered safe and effective.

Experts still advise the public to use sunscreen.

"Studies need to be performed to evaluate this finding and determine whether there are true medical implications to absorption of certain ingredients," said Yale School of Medicine dermatologist Dr. David Leffell, a spokesman for the American Academy of Dermatology.

"The sun is the real enemy here," said Scott Faber, senior vice president for government affairs at the Environmental Working Group, or EWG, an advocacy group that publishes a yearly guide on sunscreens.

"It's not news that things that you put on your skin are absorbed into the body," Faber said. "This study is the FDA's way of showing sunscreen manufacturers they need to do the studies to see if chemical absorption poses health risks."

According to the Skin Cancer Foundation, hundreds of Americans are diagnosed with skin cancer every year than all of the other cancers combined. Melanoma ranks as the 19th most common cancer in both men and women around the world, according to the World Cancer Research Fund.

"It's important for consumers to know that for the purpose of this study, sunscreens were applied to 75% of the body, four times per day for four days -- which is twice the amount that would be applied in what the scientific community considers real-world conditions," said Alex Kowcz, chief scientist for the Personal Care Products Council.

The American Academy of Dermatology recommends the public to apply at least one ounce of sunscreen to all of the exposed skin after swimming or every two hours. The places that need to be applied are the face, back, neck, top of your feet and legs and ears. If you have thinning hair or no hair at all, you can apply sunscreen on your scalp, or you can wear a hat.

You can also protect your lips by applying a lip balm with SPF 15 or above. Sunscreens should still be applied even on cloudy days and winter time because UV rays are always present.