Humans and mice with natural red hair have elevated basal pain thresholds and an increased sensitivity to opioid analgesics.
Prior research has already put red-haired humans and mice into the spotlight, pointing out that they have a higher pain threshold. They also don't need as high of a dosage of pain-killing opioids, and they tend to require more anesthesia compared to people with non-red hair.
The researchers conducted their experiments using a strain of red-haired mice that carry the MC1R variant also found in people with red hair. The mutation suppresses function of the melanocortin 1 receptor. These mice show higher tolerance to pain.
Previous studies have found that individuals with red hair, as well as those with the corresponding melanocortin-1 receptor (MC1R) mutations, exhibit a greater resistance to the effects of systemic and local anesthetics.
Less expectedly, red hair is also associated with pain sensitivity, endometriosis, Parkinson's disease, decreased platelet function and, perhaps, defects in the immune system [2–11]. These associations seem to involve a risk factor not directly related to fairness of skin and vulnerability to UV.
Her research lead all the way back to the ginger gene's origin in Africa, tracing its spread across ancient Greece, to the redheaded mummies of China, and to Renaissance Europe. Colliss Harvey's research found that redheaded individuals have higher levels of vitamin D, which is a source of strength.
While some studies suggest a potential link between certain genetic variations and alcohol metabolism, the idea that redheads universally have a higher alcohol tolerance remains inconclusive and should be approached with caution.
The gene responsible for red hair (MC1R) also releases a hormone that is similar to endorphins which limit the feeling of pain. This means that redheads need less painkillers to treat ailments.
However, in a separate study, people with MC1R variants were less sensitive to stimulus from electrical currents. This was followed by a small study published in the journal Anesthesiology, which found that women with red hair required up to 20% more anesthesia to keep them sedated than did women with dark hair.
Women with red hair color exhibited higher sexual desire and sexual activity, a higher number of sexual partners of the preferred sex, earlier initiation of sexual life, and lower sexual dominance (and therefore higher sexual submissiveness).
Genetic Background
Variants of this gene not only result in the characteristic red hair and fair skin but also influence pain perception and drug metabolism. Research has shown that these genetic differences can lead to variations in how redheads respond to anesthesia, painkillers, and other medications.
Collectively, people with red hair were rated as most unattractive, but it must be noted that in the non-obese woman condition, red hair was seen as equal to blond hair in attractiveness, though in every other condition red hair was seen as significantly less attractive.
Previous studies have also reported that red-haired individuals are more sensitive to thermal pain and dental pain (Binkley et al., 2009; Liem et al., 2005) and that individuals carrying MC1R variants associated with a red-hair phenotype have increased requirements for anesthetics (Liem et al., 2004) or increased fear ...
Especially female redheads are known to suffer higher pain sensitivity and higher incidence of some disorders, including skin cancer, Parkinson's disease and endometriosis.
One of the many facts about redheads is that their hair will never turn grey. The pigment in their hair that causes it to be red will just fade over time, causing their hair to turn blonde or white, but never grey.
In summary, redheads are more sensitive to thermal pain than women with dark hair but do not show differences in baseline electrical pain thresholds. Furthermore, redheads are more resistant to the analgesic effects of subcutaneous lidocaine.
Genetics, namely two copies of the MC1R gene, can put people with red hair at a higher risk of skin cancer. They may also be at a higher risk of developing colorectal, ovarian, or cervical cancers.
Overall, research on redheads supports the seeming contradiction that they have a higher tolerance for pain in general, but they have increased sensitivity to certain types of pain. For example, one study found women with red hair were more sensitive to temperature-related pain compared to women with dark hair.
Perhaps bruises are more noticeable in those with fair skin. Differences in vascular fragility and non-detectable haemostatic factors, or simply redhead-specific female clumsiness, cannot be excluded. Anaesthetists are right though, redheads are different: they have greater anesthetic requirements than non-redheads.
Women with red hair color exhibited higher sexual desire and sexual activity, a higher number of sexual partners of the preferred sex, earlier initiation of sexual life, and lower sexual dominance (and therefore higher sexual submissiveness).
According to some research, redheads may need larger doses of some painkillers, such as opioids, because of variations in how these medications are metabolized by their bodies.
Genetics of alcohol dehydrogenase indicate resistance has arisen independently in different cultures. In North America, Native Americans have the highest probability of developing an alcohol use disorder compared to Europeans and Asians.