Why do you itch and should you scratch?
When it comes to the science of the itch, we’ve only just scratched the surface of this medical mystery. As we discover on The Curious Cases of Rutherford & Fry, this overlooked area of medicine is revealing surprising results about the human brain.
Here are a dozen facts that will really get under your skin:
1. Rough estimates suggest you scratch an itch about 97 times a day
You probably have one or two now. Go on, nobody’s looking.
2. Itches caused by insects or plants are triggered by toxins left in your skin
The toxins start the release of histamines, part of your body’s immune response. This causes nerve fibres to send itchy signals to your brain.
3. Itches have their own nerve network
Until recently we thought that itch and pain both shared the same pathways, but in 1997 a ground-breaking discovery revealed that the itch has its own specialised nerve fibres.
4. But itch signals travel really slowly
Nerve fibres all have different speeds. Touch signals speed along at 200 mph. “Quick pain” (which you experience if you accidentally touch a hot cooker) travels at 80mph. Itches crawl along at 2 mph – slower than walking pace.
5. Itching is contagious, just like yawning
Scientists proved this by showing a set of mice videos of other mice scratching. The first group started having a quick scratch too.
6. Contagious scratching involves a tiny part of your brain called the suprachiasmatic nucleus
Neuroscientists currently have no idea how this part of your brain is involved in seeing and spreading scratchy behaviour.
7. Scratching is the best way for your body to deal with itchy invaders
It helps bat away any pesky insects or poisonous plants. It also makes your blood vessels expand, letting white blood cells and plasma flood in to wash away the invading toxin. This is why your skin becomes red and blotchy.
8. Scratching feels pleasurable because it releases serotonin in the brain
9. The nicest place to scratch is your ankle
Research has shown this to be the case. And you have probably just scratched your ankle to check.
10. The more you scratch, the more you itch
Beware the itch-scratch cycle! Scratching your skin releases extra histamine, sending more itchy signals to your brain. Do it too much and you will break the skin, risking infection and causing nasty scabs.
11. The itch-scratch cycle is problematic in skin conditions like psoriasis and eczema
Antihistamines are often prescribed to try and reduce the effects of histamine and combat itchy sensations.
12. Chronic itch has been shown to be as debilitating as chronic pain
It has been linked to many conditions such as liver disease and lymphoma.
Posted, but not written by, Lou Sheehan