Byline: Dipti. Bhute, Bhavana. Doshi, Sushil. Pande, Sunanda. Mahajan, Vidya. Kharkar

Introduction

Dermatographism also called as skin writing, dermographism or dermatographic urticaria is an enigma for dermatologists and immunologists alike. Although simpler to elicit, its clinical relevance or significance is yet to be fully known. When normal skin is stroked with a dull object, it becomes raised and inflamed to assume the shape of the stroke.[sup] [1] The response consists of local erythema followed by edema and a surrounding flare reaction. Exaggeration of this response is known as dermatographism. Dermatographism can appear in persons of any age but is more common in young adults. Peak incidence is in the second and third decades of life.

Symptoms of itching, rash and whealing are induced by scratching, stroking, tight or abrasive clothing or other personal wear. Rubbing, minor pressure or any form of physical stress to the skin may initiate lesions. Scalp, genitalia, mucocutaneous junctions and mucosae are involved less frequently.

How to Elicit Dermatographism

The diagnosis is usually made by observing the clinical response after using moderate pressure to stroke or gently scratch the skin [Figure 1]. The site of elicitation of dermatographism is important as areas protected from regular pressure and environmental influences are more reactive than others. For this reason, dermatographism is elicited more markedly over the trunk as compared to the limbs.

As the pressure of a stroke has inter-individual and intra-individual variations, a calibrated instrument known as a dermographometer can be used for applying uniform pressure over the skin. It has a spring-loaded stylus that applies graded and reproducible pressure (of 3600 g/cm[sup] 2 ) over the skin and then records skin responses. Although, it can also be used in children effectively, its current use is limited to research settings.

Pathophysiology of Dermatographism

Firm stroking of the skin produces an initial red line (capillary dilatation) followed by an axon-reflex flare with broadening erythema (arteriolar dilatation) and the formation of a linear wheal (transudation of fluid/edema). This is termed as the triple response of Lewis. An exaggerated form of this response is known as dermatographism. Unfortunately, the so-called exaggeration is highly subjective and thus not enough to distinguish between dermatographism and the triple response of Lewis with precision and surety. The time needed for the response to occur after stroking may help to some extent. Dermatographism usually develops within five minutes of stroking the skin and persists for 15-30 min in contrast to the normal triple response of Lewis that...