Itching and Tickling Sensations
Tickling and itching are both sensations caused by stimulation of the integumental surface of the body. Tickling refers to the tingling sensation that is produced by a light moving type of touch on the skin. Any number of objects contacting the skin, from fingers to a feather can cause the sensation. If the touch becomes harder, the tickling sensation can be replaced by pain.
An itch is an irritable sensation that is caused by the stimulation of nerves in the skin that are sensitive to pain. But the responses to these two stimuli differ; humans draw away from the source of pain, but will scratch at an itch. The basis of this difference in the same nerve is still unclear.
Itching is also known as pruritis. The sensation of itching is produced by a number of causes. Chemicals can react with the skin and perturb the surface cells. Poison ivy is an example of such a chemical form of itching. The bite of a mosquito can cause lesions on the skin. The lesions are often itchy. Some allergic reactions can also produce an itching sensation, because of chemicals such as histamines that are released in the immune response to the allergen. Hives is an example of an allergic type of itching. Exposure to asbestos is another example. Another type of itching occurs when the skin is perturbed, as happens by a few days growth of facial hair in some males, and in fungal infections such as athlete's foot. Other infections can cause itching. An example is scabies, which is caused by the burrowing of a mite underneath the skin.
An automatic response to itching can be to scratch the offending region. Unfortunately, this usually only succeeds in irritating the skin more and making worse (exacerbating) the problem.
The ticklish sensation can also be unpleasant. Indeed, in the Middle Ages, tickling was used as a form of torture. More often though tickling is associated with laughter. The physiochemical basis of the laugh response is still unclear. It may be related to the release of endorphins in the brain. Depending on the individual, susceptible areas of the body include the underarms, waist, ribs, bottom of the feet, back of the knees and the neck. Tickling depends upon the element of surprise. Someone cannot usually tickle himself or herself, for example. This may be related to the sensing of movement by the cerebellum region of the brain.
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