Between 1970 and 2009, the rate of melanoma among women increased eightfold and quadrupled among men, according to Mayo Clinic experts who studied all medical records for 256 people in a county in Minnesota over that time span.

However, death rates from melanoma fell during the same period, suggesting that early interventions may be helping to save some lives, said the researchers.

And while the results of the small study may not be representative of the entire United States, lead investigator Jerry Brewer, a Mayo Clinic dermatologist, sounded the alarm about what he called a "dramatic rise in women in their 20s and 30s."

"There is no such thing as a healthy baseline tan," Brewer said.

"Even though young people have more of an understanding of the detrimental effects of tanning they are still not changing their behaviour and they are tanning just as much or more as they did way back in the '80s."

Although the current study did not focus on reasons for the increase, Brewer said other researchers have found that people who use indoor tanning beds – a $5 billion dollar-a-year industry – are 74% more likely to get melanoma than non-tanners.

Jennifer Stein, a dermatologist at New York University Langone Medical Centre, agreed that indoor tanning is a likely culprit.

"One possible explanation for this rapid increase in cases of melanoma may be the use of indoor tanning beds in teens and young adults, which has become so popular in recent years," said Stein, who was not involved with the study.

"It's important for people to protect their skin from ultraviolet exposure, and to check their skin for new or changing moles, which can be a sign of melanoma. The key to surviving melanoma is early detection."

Melanoma is the deadliest form of skin cancer, and is expected to cause 76 000 new cases and 9 100 deaths in the US this year, according to the National Cancer Institute.

People at the highest risk are those with light hair and green or blue eyes. Spending a lot of time in the sun,. and having had one or more blistering sunburns in youth also boost the risk.

One young woman affected by skin cancer is Laura Hopwood, a 22-year-old network technician from New York, who was recently diagnosed with melanoma and had a pea-sized cancerous mole removed from her left cheek.

A second precancerous mole has also been found and removed, and she now faces a lifetime of vigilance against skin cancer even though she has never used an indoor tanning bed but is blond-haired, blue-eyed and has more than 50 moles on her body.

"I was out in the sun as a kid and I didn't wear as much sunscreen as I should have because that wasn't necessarily on my mind. I also had that perception -- skin cancer happens to old people, it doesn't happen to me," she told AFP.

"Young people need to be aware it is on the rise, particularly among women just like me," she added, urging people to check their moles regularly for any signs of change and protect themselves from the sun.

Hopwood now regularly sees a host of doctors who check her blood levels and moles twice a year to make sure there is no sign of the cancer returning.

One of her dermatologists, Kavita Mariwalla of Beth Israel Medical Centre in New York, said she is seeing more and more young patients like Hopwood.

"In the recent five years it has been a steep increase," Mariwalla told AFP.

"If you go to a high school prom these days every single person is tan," Mariwalla said, adding that popular television shows like Jersey Shore have instilled the notion that tanning – like going to the gym and doing laundry – is an acceptable part of daily life.

"They are making this unsafe behaviour part of their pattern," she said. "It puts them at risk for the rest of their life. If you have one skin cancer you have a 40% chance of developing a second one within five years."

Doctors urge people to limit sun exposure, use sunscreen, and check moles for the ABCDEs: asymmetry, a border that is blurred or irregular, colours that are varied within the same mole, a diameter of more than a pencil eraser, and elevation or evolution – signs that the mole is raised or is changing shape.