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A condition in which the skin is peculiarly susceptible to irritation, characterized by elevations or wheals with surrounding erythematous axon reflex flare, caused by tracing a fingernail or a blunt instrument over the skin.



a reaction of the cutaneous blood vessels manifested by a red (dermographia rubra) or white (dermographia alba) line where the skin has been scratched.

Dermographia occurs in everyone. Dermographia alba appears during spasm; pronounced dermographia rubra, upon dilation of the capillaries in the irritated area. The appearance of dermographia rubra or alba also depends upon the amount of pressure with which the irritation is applied: dermographia alba appears five to 20 seconds after a light scratch; dermographia rubra, when greater pressure is applied. Dermographia is used to study the state of the autonomic nervous system, which innervates the blood vessels: the appearance of dermographia alba after either light or strong pressure indicates that sympathetic nervous tone is predominant; the appearance of dermographia rubra is indicative of the predominance of parasympathetic tone. In some cases (for example, in exhaustion) dermographia may not appear at all. Determination of the nature of the dermographia is important in the diagnosis of a number of diseases of the nervous and endocrine systems.

References in periodicals archive ?
A Dermatographism is a skin condition which affects up to five per cent of the population.
Consider dermatographism as a possible cause of vulvovaginal pruritus, especially in severe, persistent cases that are unresponsive to antifungal drugs, Dr.
Of these, 44 "did not meet study inclusion criteria," 32 declined to participate (probably to avoid suffering another attack), 9 were lost to follow-up, one was pregnant, and one had dermatographism.
In vitro tests of food-specific IgE antibodies are often used in patients with extensive skin disease, significant and prolonged dermatographism, or a history of exquisite sensitivity (i.
They are minimally invasive, with no risk of an adverse reaction in the patient, and are the best option in patients with severe skin conditions such as eczema, urticaria, or dermatographism.
Clinically, pruritus and dermatographism are often present.