You Asked ...
What's an itch and why does it go away after you scratch it?
Jennifer Kaufman, 14 Mobile, Ala.
Here's an answer that may make you scratch your head. "The best definition science can come up with for itching [or pruritus] is a sensation that makes you want to scratch," says Stephen Webster, a dermatologist (skin expert) at Gunderson Lutheran Medical Center in LaCrosse, Wisconsin. "We still don't know everything about what makes you itch." Some scientists think you can get itchy just thinking about it.
An itch usually occurs when skin becomes irritated. Common skin irritants: mosquito bites, bee stings, poison ivy, and other allergens--compounds that cause allergic reactions, which range from strawberries to chocolate to pets. Allergens can trigger the body's release of an excessive amount of chemicals including histamine, that dilates or expands blood vessels. This lets more blood flow to the irritated area, Webster explains, and produces bumpy red rashes or hives, forms of skin inflamation called dermatitis. Skin damage like dry skin and sunburn can also induce an itch.
Then, scientists think, nerve fibers called cutaneous sensory neurons signal the brain with a "SCRATCH ME HERE." A scratch may relieve a minor itch like a bug bite, because scratching disperses (spreads out) histamines, Webster explains. This temporarily slows histamines from interacting with the affected spot. But in more severe cases of dermatitis, a scratch can inflame an irritation and make you itch more. "It's like hitting a broken leg with a hammer," says Webster. "You don't give your skin a proper chance to heal."
A cold compress or rinsing irritated skin in cool water may be the oldest way to ease an itch. Common ingredients like camphor or menthol in over-the-counter ointments can numb sensory nerve endings and mask an itch with a tingling sensation. For more severe irritations, oral antihistamines can prevent the release of histamines. While it's tempting to scratch an extremely painful case of dermatitis, for a speedy recovery, try to remember: HANDS OFF!
HAVE A SCIENCE QUESTION?
Send it to: You Asked! Science World 555 Broadway New York, NY 10012
Include your name, age, school name, address, and phone number.
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||question about itching and scratching|
|Date:||Oct 16, 2000|
|Previous Article:||You Can Do It.|
|Next Article:||DEAR TEACHER:.|