Blondes may have more fun, but do redheads feel less pain?

Hair color has always had interesting stereotypes associated with it. For instance, almost everyone has heard a hundred times that blondes have more fun, or they've heard the (untrue) joke about "dumb blondes" and the things they do. Brunettes have the "girl next door" stereotype, or they're thought of as clever and confident. Redheads are typically thought of as hot-tempered, and recently, many people have been quite vocal about how redheads have a higher pain tolerance than most people. The question is, is any of this true? After all, many of us grew up hearing various nursery rhymes and old wives' tales that have no basis in reality. Chocolate doesn't lead to acne (unless you rub it all over your face), and despite making many silly faces you never see anyone walking around with their face permanently frozen in a goofy expression. However, recent medical discoveries may show that there's some basis to at least some of the stereotypes behind hair color. The assertion about redheads' pain tolerance is actually one that may be founded in medical science. Being a redhead is a genetic mutation that results in a non-functional melanocortin-1 receptor (MCR-1) (Mogil et al. 2005). This change in receptor results in an overexpression of pheomelanin, which results in red hair color (Liem et al. 2005). In addition to having control over the pigmentation of redheads, it also has interesting affects on pain reception response to commonly used anesthetics. MCR-1 has an effect on the perception of κ-opioid and μ-opioid receptor-mediated anesthetics (Mogil et al. 2005). This mutation in the receptor has interesting effects on the pain tolerance of redheads and their response to analgesics. Rumor has it that redheads have higher pain tolerance than people with other hair colors. However, when this was actually put into practice, red-headed women were found to have about the same current perception, pain perception, and pain tolerance thresholds as dark-haired women (Liem et al. 2005). However, it gets interesting when redheads' other tolerances are compared to those of dark-haired people. Redheads have more perception of pain associated with cold, pain associated with heat, and they also have a lower cold perception threshold (Liem et al. 2005). However, their mutated receptors also have a strange effect on how analgesics work on them. Lidocaine is an example of one of the drugs whose interaction is changed by this mutated receptor. When injected, subcutaneous lidocaine proved less effective in redheads as compared to people with dark hair, as redheads reported pain from 2000 Hz stimulation at 11.0 mA, while women with darker hair reported pain at >20 mA (Liem et al. 2005). In another study, redheads and brunettes were sedated with sevoflurane and then the sedation was maintained with desflurane, and then a noxious stimulus was administered through intradermal needles (100 Hz, 70 mA) (Liem et al. 2005). The effect of the sedation was monitored through the person's response to the stimulus: if the person moved, then the anesthetic was deemed ineffective and the dosage of desflurane was increased, and if the person did not move in response to the stimulus four times, then the sedation was deemed effective and the dosage was noted (Liem et al. 2005). Redheads needed higher desflurane leves in order to stay sedated (Liem et al. 2005). How is this at all significant in any way (in any other way besides confirming or debunking an old wives' tale)? Lidocaine is typically used topically as a method of sedation (Smith and Wilson 2013). Topical sedation typically allows the patient to remain awake during the procedure, or it can be used in addition to injectable anesthetic. The use of lidocaine is particularly important in surgeries where it is important to be conscious while the procedure is going on. For example, in a recent case study a woman presented with an endotracheal mass that caused breathing problems (Loizzi et al. 2013). In this case, lidocaine was an essential part of the procedure because it allowed the movement of the vocal cords during the surgery and thus they were not damaged in the procedure (Loizzi et al. 2013). It is important for surgeons and physicians to keep in mind that redheads have a higher tolerance for pain medication such as lidocaine so that there are no cases of the patient experiencing discomfort during a procedure. Old wives' tales may not make a lot of sense sometimes, but at others they have a basis in truth. Redheads do have an increased tolerance to anesthesia, but are more susceptible to pain from heat or cold. It is important for physicians to stay aware of groups that may experience pain during surgery if inadequately sedated so that patients remain satisfied with their care. References Liem EB, Joiner TV, Tseuda K, Sessler DI. 2005 Mar. Increased sensitivity to thermal pain and reduced subcutaneous lidocaine efficacy in redheads. Anesthesiology. 102(3): 509-514. Liem EB, Lin C-M, Suleman M-I, Doufas AG, Gregg RG, Veauthier JM, Loyd G, Sessler DI. 2004 Aug. Anesthetic requirement is increased in redheads. Anesthesiology. 101(2): 279-283. Loizzi D, Sollitto F, De Palma A, Pagliarulo V, di Giglio I, Loizzi M. 2013 Mar. Tracheal resection with patient under local anesthesia and conscious sedation. The Annals of Thoracic Surgery. 95(3): e63-e65. Mogil JS, Ritchie J, Smith SB, Strasburg K, Kaplan L, Wallace MR, Romberg RR, Biji H, Sarton EY, Fillingim RB et al. 2005 Jan. Melanocortin-1 receptor gene variants affect pain and μ-opioid analgesia in mice and humans. Journal of Medical Genetics. 42:583-587 doi:10.1136/jmg.2004.027698 Smith BC and Wilson AH. 2013 Jun. Topical versus injectable analgesics in simple laceration repair: an integrative review. The Journal for Nurse Practitioners. 9(6): 374-380.