AAAAI - Patients & Consumers Center: Allergy & Asthma Issues: Fall 2009

FLU, ASTHMA AND ALLERGIES
Veneta Ianakieva, BS and Richard W. Honsinger, MD, MACP, FAAAAI

An itch can be brought on by allergies, dry skin, insect bite, stress or, in some cases, a serious medical condition.

While most itches are merely bothersome or uncomfortable, excessive scratching can damage your skin’s protective barrier and expose your body to germs and infection.

Itch and pain are closely linked in the brain. The reflex to pain is to withdraw. The reflex to itch is to scratch. Itch sensations are rooted in our evolution. It is a protective response developed to help animals remove parasites from their skin. That’s why even a slight movement of hairs is enough to make you want to scratch.

Itching is often triggered by histamine, a protein in the body associated with immune responses. Among other roles, histamine is released during an allergic reaction. It causes the itch and redness you see with insect bites, rashes and skin dryness or damage.

Histamine is also released by the body during allergic reactions, such as those to food and medications. If your itch is accompanied by a rash, it may be caused by an allergy. An allergist/immunologist can identify the triggers and prescribe treatment.

TYPES OF ITCH
Pruriceptive itch is due to an allergy reaction, inflammation, dryness, or other skin damage. It is seen in atopic dermatitis (eczema), urticaria (hives), psoriasis, drug reactions, mites, and dry skin. This type of itch is treated with antihistamines and drugs that alter the immune reaction.

Neuropathic itch is caused by damage to the nervous system. It is usually accompanied by sensations of numbness and tingling. This type of itch is seen after shingles (postherpetic neuralgia), after stroke or burn injury, and in notalgia parasthetica (an area of itchy skin, usually on the back). It is treated with non-narcotic analgesics and capsacin.

Neurogenic itch originates in the central nervous system in the absence of nerve damage. This type of itch is seen in chronic liver and kidney disease in response to opioid neuropeptides. It is treated with narcotic and non-narcotic analgesics.

Psychogenic itch is induced in response to the chemicals serotonin and norepinephrine. It is observed in stress, depression, and delusional parasitosis (a false belief of parasite infestation). Psychogenic itch is treated with antidepressants and antipsychotic medications.

If itching (with or without a rash) is affecting the quality of your life, consult your physician to find the underlying cause and get relief.

About ISSUES

Allergy & Asthma Issues is a free quarterly publication from the American Academy of Allergy, Asthma & Immunology.

Issues is written and reviewed by medical professionals, but is not intended to replace or constitute medical advice. For specific medical questions, visit an allergist/immunologist. Locate one near you at www.aaaai.org/physref.

For additional patient information on allergies and asthma, visit www.aaaai.org.

The American Academy of Allergy, Asthma & Immunology represents allergists, asthma specialists, clinical immunologists, allied health professionals and others with a special interest in the research and treatment of allergic disease. Established in 1943, the AAAAI has nearly 6,500 members in the United States, Canada and 60 other countries.