Joey Nelson has always loved the sun. “I sailed growing up,” he says. “Every Saturday we’d go and I’d get sunburned like crazy, not even thinking about putting on sunscreen.”

With fair skin, red hair and moles, Joey was already at increased risk for skin cancer, so he wasn’t exactly surprised by his melanoma diagnosis. The skin cancer first showed up on his leg in 1986.

After having the melanoma removed with a skin graft...