Itch

Skin | Dermatology | Itch (Disease)


Description

Itch is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to classify it as any one type of sensory experience. Modern science has shown that itch has many similarities to pain, and while both are unpleasant sensory experiences, their behavioral response patterns are different. Pain creates a withdrawal reflex while itch leads to a scratch reflex. Unmyelinated nerve fibers for itch and pain both originate in the skin; however, information for them is conveyed centrally in two distinct systems that both use the same nerve bundle and spinothalamic tract.

Itches are a common problem and can be localized (limited to one area of the body) or generalized (occurring all over the body or in several different areas). In some cases, itching may be worse at night. The medical term for itching is pruritus.

Depending upon the underlying cause, itching may be associated with other symptoms and signs. Most commonly, these associated findings include skin lesions such as rash, blisters, bumps, or redness of the affected area. Dryness of the skin is a common cause of itch. Itching of skin can lead to tears in the skin (excoriations) from scratching. Less commonly, generalized itching can be a sign of chronic medical conditions such as liver disease. In these situations, there may be no changes to the appearance of the skin.

Causes and Risk factors

Itching can be caused by many conditions. A common cause of itch is psychological, that is, due to stress, anxiety, etc. Stress also can aggravate itch from other causes. Dry skin (xerosis) is another frequent cause of itch. Many people also report sunburn itch following prolonged exposure to UV radiation from the sun. Other causes of generalized itching that may not produce a rash or specific skin changes include metabolic and endocrine disorders (for example, liver or kidney disease, hyperthyroidism), cancers (for example, lymphoma), reactions to drugs, and interruptions in bile flow (cholestasis), diseases of the blood (for example, polycythemia vera). Itching is common with allergic reactions. Itching can also result from insect stings and bites such as from mosquito or flea bites.

Infections and infestations of the skin are another cause of itch. Genital itching, which may accompany burning and pain, in men and women can occur as a result of genital infections such as sexually transmitted diseases (STDs).

Diagnosis and Treatment

An itch that is accompanied by a visible skin abnormality usually should be evaluated by a physician and, in some cases, by a dermatologist since the problem is likely to be a condition that requires specialized medical treatment (for example, eczema, scabies, etc). Topical antipruritics in the form of creams and sprays are often available over-the-counter. Oral anti-itch drugs also exist and are usually prescription drugs. ...