Dermographism - reaction vessels of the skin on mechanical irritation. Distinguish between local and reflex dermographism (Fig. 5-8).

Fig. 3. White dermographism. Fig. 4. Red dermographism. Fig. 5. Sublime dermographism. Fig. 6. Reflex dermographism.

The first is a local reaction vessels; cause it dashed skin irritation blunt object. In low pressure appears white band, with a strong red. White dermographism occurs when a spasm, and red with the expansion of capillaries of the skin. Sometimes red dermographism becomes exalted dermographism. If the weak and under strong pressure occurs white dermographism, this means that the prevailing tone of the sympathetic innervation, if there is a red dermographism - tone prevails parasympathetic innervation. Change dermographism can be seen in a vegetative dystonia, meningitis, thyrotoxicosis and other diseases. No dermographism often observed in severe poisoning nervous system, exhaustion and other pathological conditions.
Reflex dermographism is spinal reflex; cause it dashed holding the leather tip of the needle. The arc of this reflex passes through appropriate spinal segments. Reflex dermographism missing with the defeat of the back and front of the roots of the spinal cord, his horns lateral, and also in case of peripheral nerve inflammation, trauma, tumors).