Only 1-2% of all humans are redheads. With this uniqueness comes some inherent health concerns. These vary from increased risk of skin disease, Parkinson's disease, and now there is evidence that suggests natural red hair is correlated with an increased need for anesthesia. The expression of red hair in almost all red haired individuals is due to a mutation in the melanocortin-1 receptor (MC1R) gene. A mutation in this gene causes production of phoemelanin instead of eumelanin which affects the production of pigment in the body. Normally among humans, anesthetic requirement is usually uniform and is mostly affected by age and body temperature. However, studies show that redheads may require up to 20% more local and general anesthesia in pain treatments than non-redheads. A study by a group of anesthesiologists and researchers showed that natural redheads with the MC1R gene mutation required 6.2% concentration of desflurane, a gas anesthetic, before they stopped "feeling" pain in the form of electric shocks. This value is 20% higher than what was found for non-redheads at a 5.2% concentration before they stopped responding to the pain. Studies have also found that redheads experience more pain during dental procedures and are resistant to lidocaine, a local anesthetic. In addition to requiring more anesthetics, those with the MC1R mutation are also more sensitive to pain in regards to temperature and are twice as likely to have anxiety about dental care due to the increased pain. A mutation in this gene can affect more than just redheads, however. It is possible for non-redheads to have this mutation and is more likely in individuals who have pale skin and lighter hair. It is still unknown exactly why the mutation of the MC1R gene causes these effects in regards to anesthesia, however there are speculations on what it could be. One such theory is that MC1R mutations produce an increased response of melanocortins that increase pain sensitivity in individuals due to stimulation of melanocortin receptors.