Over the last few decades, research has found that people with red hair might experience pain differently than people with other kinds of hair.

The link appears to be rooted in genetics. Red hair is caused by a mutation of the melanocortin-1 receptor (MC1R), a type of gene responsible for producing pigment for skin and hair.

An MC1R mutation may be involved in pain as well. It might also affect a person’s response to anesthesia, which is given before procedures to prevent pain.

However, there’s some disagreement on the link between redheads and anesthesia, as the available studies have found mixed results.

Read on to learn about what the science says so far.

Types of anesthetics

There are several types of anesthesia to consider:

  • General anesthesia. General anesthesia is administered by a healthcare professional through a mask or intravenously (IV). It puts you to sleep and is typically used for longer surgical procedures.
  • Local anesthesia. Local anesthesia is used to numb a small area of skin during a minor procedure, like a skin biopsy. It can be applied topically or through an injection. You remain alert during local anesthesia.
  • Regional anesthesia. This is used to make a specific part of the body numb to relieve pain or allow for surgical procedures to be performed on it.
  • Epidural. An epidural is a common type of anesthetic used for pain relief during labor.
  • Spinal anesthesia. Also called a subarachnoid block, this is a type of regional anesthesia for the spine.
  • Nerve blocks. Nerve blocks are a type of regional anesthesia that interrupt signals traveling along a nerve.

The relationship between red hair and pain is still unclear. The research is ongoing, and currently available studies have found conflicting results.

Here’s what the research has found thus far:

MC1R gene and pain sensitivity

As mentioned earlier, red hair is due to MC1R mutations.

Nearly 20 years ago, researchers found that MC1R gene variants are involved in pain. In a 2005 study, researchers examined the link between MC1R variants and pain sensitivity. They tested pain by administering electrical currents.

They found that those with MC1R variations were able to tolerate greater electrical currents. This suggested that two MC1R variants are linked to lower pain sensitivity.

In contrast, researchers in another 2005 study found that people with MC1R mutations have a higherpain sensitivity. But this experiment used thermal pain (heat and cold) instead of electrical currents.

Finally, a 2020 study suggests that the MC1R variants related to pain sensitivity might actually be different than the variants that cause red hair.

More research is needed to confirm how MC1R mutations affect pain sensitivity and whether it depends on the type of pain.

MC1R gene and anesthesia

Lidocaine is an anesthetic that can be applied topically or subcutaneously (injected into the skin). It’s used as a local anesthetic to prevent pain during procedures.

In the 2005 study using thermal pain, the researchers examined the effect of lidocaine in people with red and dark hair. Both groups had a similar response to lidocaine that was applied topically.

However, subcutaneous lidocaine yielded different results. The participants with red hair experienced a lower response than those with dark hair. In other words, lidocaine was less effective in those with red hair.

These findings suggest people with red hair may need higher doses of anesthesia.

Anesthesia vs. analgesics

Interestingly, compared to anesthesia, analgesics appear to affect people with red hair in a different way.

In a 2005 study using electrical currents, researchers found that those with MC1R mutations had a higher response to opioids. Opioids are analgesics, also known as pain relievers.

The greater response suggests that people with red hair might need lower doses of analgesics.

Researchers study pain levels using various methods. Depending on the study, this may include:

  • Self-reported ratings. After administering a form of pain, researchers ask participants to rate their pain on a given scale. For example, in a 2020 study, people rated their pain on a scale from 0 to 100. In this study, a higher number indicated more pain.
  • Scripted responses. In this technique, the researchers provide people with responses to describe their level of pain. This method was used in the 2005 study involving thermal pain.
  • Pressing a button. In some studies, people are asked to press a button when the pain stimulus is no longer tolerable. The measurement of the pain stimulus at that point will indicate the person’s pain level.

Researchers are still learning about how anesthesia affects people with red hair. If redheads do need higher doses of anesthesia, there are some possible health effects to consider.

Specifically, the usual amount of anesthesia given before procedures might not be enough to prevent pain in redheads. This may pose complications like:

  • fear or discomfort at the dentist because anesthesia doesn’t work as well
  • difficulty preparing for surgeries
  • poor response to prescribed anesthetics, like topical lidocaine for sore throats

Depending on the procedure or treatment, your healthcare professional will administer a specific dose of anesthesia. This dose will be based on several factors, like your age and type of anesthesia. The specific dose is also designed to deliver a safe amount of anesthesia.

However, if you’re given too much, you might experience the following side effects:

  • dizziness
  • muscle weakness
  • metallic taste in your mouth
  • double vision
  • low blood pressure
  • seizures

The link between red hair and anesthesia is still being studied. There’s some evidence that the MC1R mutation, which causes red hair, is also involved in one’s response to pain and anesthesia.

If redheads need more anesthesia, it might make certain surgical preparation more difficult, but additional research is needed.

If you have red hair and are concerned about receiving anesthetics, speak with your doctor.