Redheads' fair skin has long meant that they were at increased risk for burning in the sun. However, amidst evidence that their genes may put them at an increased risk for skin cancer regardless of the presence of the sun, a new study indicates that as many as 40 percent of Europeans harbor recessive redhead genes. Researchers currently worry that these "silent redheads" could be at increased risk for many of the health problems that are elevated in redheaded individuals.

The study was conducted with the DNA of 5,000 Britons. In England, 6 percent of the population has red hair; that statistic goes up to 13 percent in Scotland. In mainland England, that number settles down to 4 percent. Red hair generally appears more prevalently in cloudy climates, where pale skin helps people soak up all the available Vitamin D. Red hair is caused by a gene that changes the behavior of the MC1R protein.

Despite the fact that red hair itself is not altogether common, the study found that 4 in 10 of the people studied had the recessive gene for red hair, even if the person had no family members with red hair. However, these "silent redheads" could be at increased risk for health conditions to which redheads are predisposed.

Several studies have found that redheaded individuals have an increased susceptibility to pain. A 2004 study conducted by the University of Louisville found that redheads require, on average, 20 percent more anesthesia than people with other hair colors. Another study, this one published in the Journal of the American Dental Association in 2009, found that redheads were twice as likely to avoid going to the dentist out of fear of pain.

Other researchers wanted to cover the potential link between red hair and Tourette syndrome, a condition characterized by involuntary vocal and physical tics. The study, conducted in Australia, found that 13 percent of people with Tourette syndrome had red hair. However, only 4 percent of the general population was a redhead. Researchers want to explore whether "silent redheads" have increased risk for illness as well.

However, just because you may not have red hair on your head or in your family that does not mean your hair color does not predispose you for health conditions. People with brown hair, for example, are at increased risk for nicotine addiction because the melanin that gives individuals brown hair means that they are worse at metabolizing nicotine in their body. Blonds are at increased risk for age-related macular degeneration, which may cause blindness. People with black hair may have it the easiest though - their hair color means that they have the lowest risk of developing Parkinson's disease.