Skin care: itching


        SKIN CARE: ITCHING
An itch is one of the commonest complaints relating to the skin. Frequently it is unaccompanied by any visible causative disease. Although everyone knows what an itch is, it is nevertheless difficult to define. The most widely accepted definition might be: 'that unpleasant sensation which provokes the desire to scratch1. Itching is an important symptom of many diseases of the skin, and also of internal disorders. It also warrants attention because of the further damage to the skin that would be caused by continued scratching.
Although itching has been extensively studied, its causes are ill understood. However any discussion of itching must refer to the physiology, so that the limitations of treatment may be understood. Itching, then, is a disagreeable sensation produced by the action of stimuli of a harmful nature on the skin surface. It is a signal of actual or potential danger to the skin. The purpose of the reflex action of scratching is to remove the causative agent from the body surface.
It is thought that a wide variety of stimuli and noxious agents may liberate chemicals in the skin which then act on peripheral nerves, eliciting the itch sensation. These chemicals include histamine, bradykine, protease, and prostaglandins. Throughout the skin there are many itch receptors. On the forearm these points lie approximately one millimetre apart. However they are more closely set in areas about orifices such as the mouth or anus. The small skin nerves then carry the impulses to the spinal cord, from where they are transmitted via the pain fibres to the brain. It is not yet understood how scratching relieves itching, but possibly it disturbs the rhythm of the impulses travelling towards the spinal cord. Scratching may also simply damage the nerve fibres which are conveying the itch.
Inherent in the problem of itching is its subjective and elusive nature. Some people are Itchers, others are not. Some itch intensely, others not at all. Allowing for this variation, the absence or presence of an itch, as well as its severity, may be of great diagnostic value. Of importance, also, might be the intensity and location of the itch, as well as the time of occurrence and the factors which provoke or relieve it.
As with pain, there are always two aspects of itching—how it is perceived and a person's reaction to it. The latter has many psychological components which influence it: such factors as anxiety, tension and fear, all of which will aggravate itching. In some individuals, itching is only relieved by the infliction of self-trauma, which replaces the itching with soreness, stinging or pain. In others, itching and rubbing is associated with pleasurable emotions, which have a sexual components; this reaction is termed orgasme cutane'.
It must be remembered that an itch is a symptom not a disease, and that there are a vast number of causes of itching. However, the vast majority of individuals who itch without visible evidence of skin disease, do so for some psychological reason.

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