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The Physiology of Itching

What happens to our body when we itch, and why we feel the urge to scratch.

Brea Porter

on 17 February 2011

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Transcript of The Physiology of Itching

The Physiology of Itching Facts about itching
An itch is an irritation to the skin that elicts an urge to scratch.
The urge can be localized (one area of the body), or generalized (all over the body, or in several different areas.
An itch does not have to involve skin lesions (visual bumps or redness).
Already produced in the body as a natural defense.
Stored in cells called "mast cells" in almost all tissues in the body.
Released when the body reacts to foreign substance (allergen) How Histamine Works
* When the body reacts to a foriegn substance, it releases histamine. The histamine connects with H-1 receptors.
* This causes a chain reaction that includes increased blood flow to the area and the release of other chemicals that add to the allergic response.
* This creates a small pain that is recieved by the brain as an "itch." The "Healing Itch"
* Many theories
* Main theory: Histamine is
released after the body suffers a
small traumatic incident. The "Phantom Itch"
* A random itching sensation that comes back more than once.
* Caused by touch-receptors in the nervous system that receive specific signals. What Causes Itching
Psychological issues (stress/anxiety)
Dry skin
Sunburns (prolonged exposure to UV radiations
Matabolic/endocrine disorders (liver/kidney diseases
that cause jaundice or yellowing of skin/eyes)
Reactions to drugs, drug over use (meth)
Corruption to bile flow (cholestasis)
Diseases of the blood (polycythemia vera)
Allergic reactions
Result of insect stings/bites
Healing process
Poison oak, poison ivy
Pityriasis rosea
Fungal Infections
Jock itch
Vaginal/yeast infections
Sexually Transmitted Diseases
Summer's Itch
Pubic/head lice FACT: most people usually don't have a serious underlying condition. Why do we scratch?
Itch-scratch-itch cycle
If you break the skin, you can get a bacterial infection. Scratching can continue for multiple months, or multiple years.
The area can develop thickened skin (lichenification) or pigmentation that darkens the area. TREATMENTS Cold Applications
Cold and itch travel along the same nerve fibers.
Cold water, cool showers, ice packs. Hot water: Not reccomended, it usually leaves you itchier. Anti-itch creams and lotions
Look for over the counter remedies with:
camphor, menthol, phenol, pramoxine, diphenydramine, benzocaine, and other "caine" anesthetics.
Their job is to help numb nerve endings. Hydrocortizone-containing creams
Only helps an itch caused by a rash responsive to cortizone (eczerial seborrhea)
Very weak
Don't do anything for insect bites/stings Antihistamines
Two different generations
Sedative vs. Nonsedative
They work by blocking histamine receptors
Should not be taken by pregnant women or small children Histamine Intolerance
DAO diamine oxidase
HNMT Histamine-N-Methyltransferase Symptoms
Migrane Headaches
Gastron Testinal Symptoms
Hives, Eczema, and allergic rhinitis
Can trigger asthma attacks Treatments
Histamine-free diets
Some medications can effect DAO and HNMT
Benadryl is an immediate short-term solution if you have a sudden reaction. END
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