Growing Red-haired Kitten

Pain tolerance and injury
Two studies have demonstrated that people with red hair have different sensitivity to pain compared to people with other hair colors. One study found that people with red hair are more sensitive to thermal pain (associated with naturally occurring low vitamin K levels), while another study concluded that redheads are less sensitive to pain from multiple modalities, including noxious stimuli such as electrically induced pain.
Researchers have found that people with red hair require greater amounts of anesthetic. Other research publications have concluded that women with naturally red hair require less of the painkiller pentazocine than do either women of other hair colors or men of any hair color. A study showed women with red hair had a greater analgesic response to that particular pain medication than men. A follow-up study by the same group showed that men and women with red hair had a greater analgesic response to morphine-6-glucuronide.