The New York Times Well blog covers the growing amount of research on how the same genes that give rise to red hair also make red heads more sensitive to pain.

This has knock-on effects for doctors and dentists in that greater levels of pain killers are needed for red haired patients:

Researchers believe redheads are more sensitive to pain because of a mutation in a gene that affects hair color. In people with brown, black and blond hair, the gene, for the melanocortin-1 receptor, produces melanin. But a mutation in the MC1R gene results in the production of a substance called pheomelanin that results in red hair and fair skin. The MC1R gene belongs to a family of receptors that include pain receptors in the brain, and as a result, a mutation in the gene appears to influence the body‚Äôs sensitivity to pain. A 2004 study showed that redheads require, on average, about 20 percent more general anesthesia than people with dark hair or blond coloring. And in 2005, researchers found that redheads are more resistant to the effects of local anesthesia, such as the numbing drugs used by dentists.

Link to NYT Well Blog on ‘The Pain of Being a Redhead’.