Exposure to sun is being blamed for the rise in skin cancers
A skin cancer which is traditionally found in the over 50s is increasing among young adults, a US study says.
Researchers from the Mayo Clinic in Minnesota found incidence of the two most common forms of non-melanoma skin cancers rose between 1976-9 to 2000-3.
Researchers blamed the rise on depletion of the ozone layer, increased exposure to the sun and tanning beds, and improved methods of detection.
Cancer experts said rises had also been seen in the UK.
More than 60,000 people in the UK are diagnosed with non-melanoma each year, making it the most common cause of cancer.
But non-melanoma is usually slow growing and easily treatable - it kills just 500 people a year, compared to the 1,700 deaths caused by the much rarer melanoma skin cancer.
The US study of 485 patients aged under 40 looked at two of the most common types of non-melanoma - basal cell carcinoma and squamous cell carcinoma.
The researchers found the incidence rate rose from 18.2 per 100,000 to 29.1 over the period studied for basal cell carcinoma. The rise was particularly acute for women in their late 30s.
For squamous cell carcinoma, there was a rise from 0.9 per 100,000 to 4.1.
The report, published in the Journal of the American Medical Association, recommended people limit sun exposure and ensure they use sun cream.
Lead researcher Leslie Christenson said: "Because non-melanoma cancers generally occur in persons after 50, very little attention has been paid to their incidence in younger adults and children.
"We have discovered that these cancers are becoming increasingly prevalent in younger people, and if steps are not taken at a young age to prevent these cancers, we may see an exponential increase in the overall occurrence of non-melanoma skin cancers."
Sara Hiom, head of health information at Cancer Research UK, said: "Non-melanoma cancers are rising at an alarming rate.
"The most effective way for people to reduce skin cancer risk is to protect their skin from burning in the sun.
"Cancer Research UK's SunSmart campaign says people should avoid burning by seeking shade when the sun is at its height, covering up in a T-shirt, hat and sunglasses and applying factor 15-plus sunscreen."