In the early '50s, Coppertone began selling the first commercially successful sunscreen – and followed that up with the first sunless tanner for consumers just ten years later. Tans in a bottle and sun bathing have battled it out ever since. Neither is necessary – healthy skin trumps sun damage any day – but for those chasing a golden glow, which tanning method is healthier?

Sun tanning can cause skin cancer, premature aging, cataracts, and immune system suppression – not to mention painful burns. To avoid these consequences, everyone over the age of six months should wear sunscreen with an SPF of 15 or higher every day, according to health experts. It should be applied 30 minutes before you go outside and reapplied every two to three hours if you're in the sun. A 2010 small-scale study found that if you aren't lathering daily, you could be doubling your chance of developing melanoma, the deadliest form of skin cancer.

But if you are using the wrong brand, you may be exposing yourself to harmful chemicals. "If you're getting enough sun to get a tan, then you're getting too much," says Leffell, professor of dermatology and surgery at the Yale School of Medicine.  Just one bad sunburn significantly increases a person's risk of developing skin cancer later on.

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Once hailed as the smart alternative to tanning outside, spray tans can also be hazardous to your health. The concern stems from use of dihydroxyacetone (DHA) in tanning solutions, which interacts with dead cells on the skin's surface to evoke color change. When used properly, DHA is considered safe. "Most dermatologists agree that the spray-on tans or the tans in a bottle, which basically cause coloration of the outer layer of the epidermis – the stratum corneum – are safe and effective," says Dr. David J. Leffell.

But many people don't use spray tans properly. The FDA advises people cover their lips, nose, and eyes because the risks from inhaling DHA are unknown. Lab studies have shown that high levels of DHA – much higher than you'd find in over-the-counter tanning products – can increase free radical formation. Free radicals are part of our natural metabolic process but high levels have been linked to cell damage and cancer.

The bottom line: You may have to stuff tissues up your nose and live with pale eyelids, but if you're looking for the safest tan, a cautious application of tan in a bottle is probably best method.