How Itches Work

Scientists have classified all itches into four basic categories [source: Potenzieri]:

Pruriceptive is the most common type of itching. For the itch sensation to be triggered here, something mechanical, thermal or chemical has to stimulate the itch-sensing nerve endings on the skin, known as pruriceptors. These guys are super-sensitive. They can pick up an itchy sensation more than 3 inches away [source: Gawande].

Scientists have learned that for most types of pruriceptive itches, sensory nerve fibers called C-fibers get stimulated on the skin. They then send signals to the spinal cord and on to the brain, which generates a rubbing response reflexively from the person [source: Andrews].

The fibers are not quick to transmit the information, which is why itchiness can take so long to build up and subside. About 5 percent of the total C-fibers in human skin are connected to the itch mechanism, while many of the others are associated with pain (see sidebar on next page) [source: Andrews].

While that takes care of most itching, there are some more unusual types. Brachioradial pruritus, persistent outer-arm itching, is caused by a crimped nerve in the neck, and worsens in sunlight. Aquagenic pruritus, on the other hand, is recurrent and intense itching upon getting out of a shower. (That one is a symptom of a rare condition in which the body produces too many red blood cells.) [source: Gawande]

There is also itching that results from psychosis. People may have delusions that their skin is infested with parasites or crawling with bugs. So they scratch themselves all over.

All this talk of itching has probably made you already start scratching. We all do it. In fact, studies have shown that watching an image of someone scratching can make you want to do the same even more than watching an image of an itch-producing stimuli (like an ant crawling up an arm) [source: BBC News].

Almost all two- and four-legged animals scratch. Scientist even think that fish and fruit flies show behaviors that are probably associated with scratching when they rub up against objects (fish) or carry out robust grooming behaviors (fruit flies). But does scratching help anything?

Scratching interferes with sensations arising from pruriceptors by stimulating pain and touch receptors in same area. No one is really sure of the biochemical pathways that make scratching help the itch, but scientists have found that it has a compulsive effect on the brain. Scratching — even on places that don't itch — can activate areas of the brain associated with memory and pleasure, while at the same time suppressing those areas that are associated with pain [source: Cox].

In fact, scratching brings all sorts of relief. Long distance scratching, where you scratch far from the actual site of the itch, can even help you feel better about that itch. But if you are scratching far from the itch site, think about where you scratch. Studies show that the pleasure you get from scratching different parts of the body varies [source: Live Science].

Probably due to the way sensory nerves are distributed through the body, you get the most intense pleasure from scratching your back and ankles. And part of the key to having a scratch feel great is doing it yourself. Studies have shown that it is more rewarding to scratch your own itch than to have someone scratch it for you [source: Grady].

We can probably all agree that scratching an itch feels great. But, sadly, it's only temporary relief. Scratching can actually be more harmful than helpful if the skin becomes further irritated. So what else can you do to stop an itch?

Stopping the itch sensation is easier said than done. As we've said, itching can be due to all sorts of conditions. So you can imagine that with causes of itching ranging from a mosquito bite, to having a crimped nerve, to simply watching someone else scratch themselves, finding a cure or an end to itching is quite difficult.

So what's the best thing to do? Find out what type of itch you have to see if there's a treatment for it. You can use calamine lotion for poison ivy, hydrocortisone for eczema, or antihistamines for an allergic reaction to an insect bite.

You also can turn to your pantry for some home remedies to see if they'll do the trick. Grind up uncooked oatmeal and add it to your bath. Molecules in the oatmeal called avenanthramides block the release of inflammatory compounds, which hopefully can quell your itching. Rubbing baking soda on the skin has been known to soothe bug bites. And coconut oil has compounds that kill bacteria which can perpetuate and further aggravate an itch, especially when caused by eczema. Slather some of that on a couple times a day [source: Dog].

For psychosis-related itches, therapy might help. But how do you treat itching that is caused by some sort of neurological glitch? It's hard to determine how to handle these conditions when the underlying causes are not well understood. Antihistamines and corticosteroid treatments (like cortisone) don't work very well. Doctors currently prescribe local anesthetics that can inhibit neuronal excitability and advise their patients not to scratch [source: Oaklander].

That's actually the best advice for any type of itch, even though it's hard. Experts say to rub the spot gently, instead. That'll help the itch sensation diminish without the potential harms of scratching.