Dermographism or Factitious Urticaria
The Dermographism is a type of physical urticaria produced by physical agents which does not follows the trace of a dermatome. On Dermographism which is also known as Factitious Urticaria, the application of pressure over the skin produces a vasoconstriction followed by erythema, pruritus and a lineal inflammation.
The Dermographism is characterized by the emergence of local hives in zones of the skin that are submitted to physical friction with clothing, areas of trauma and after scratching the skin. In a much disseminated way the hives emerge in just a few minutes in the whole skin surface. The Dermographism is very frequent, it usually affects to five percent of the population approximately. Hives are eruptions of few centimeters or many centimeters of diameter, they have a whitish or reddish coloration and they are surrounded by an erythematous halo and they are frequently itching.
In the case of Dermographism like in the case of other types of urticaria, the histamine is the most important chemical product released by skin, and it is also the main responsible for itching. This condition can affect to a person at any age, although if affects more frequently young people. The beginning of the condition can be gradual although in some patients it can be developed in matter of days.
There can be identified two types of Dermographism depending on the symptomatology presented by the condition:
- It can be completely asymptomatic (simple asymptomatic Dermographism), becoming evident only during a routine check of patients. There is the theory that this is produced by an exaggerated physiological response (a constitutional trend to the formation of hives) which affects persons of any age and which persists during the whole life and has no other clinical repercussions.
- This condition can also present symptomatology (symptomatic Dermographism or Factitious Urticaria), in this case it presents an intense disseminated pruritus, which induces the person to scratch skin giving place in just a few minutes to the emergence of lineal hives in the traumatized area. The pathogeny of this condition is not known with certainty, although a positive PK has been pointed out on some patients. It is believed that the trauma over the skin can release antigens which produce an immediate allergic reaction on the traumatized zone with the subsequent releasing of histamine.
Causes and incidence of Factitious Urticaria
Although it is not demonstrated the relation between systemic diseases or allergies and some medicines and foods, probable causes that can produce Factitious Urticaria are physical exercise, the intake of foods with high content of histamine (strawberries, cheese, spinach and tomatoes among others) or medicines like nonsteroidal antiinflammatory (NSAIDs) or aspirin, progesterone and autoimmune diseases. In general there is not a unique cause for the emergence of Factitious Urticaria or Dermographism.
The Factitious Urticaria can emerge alone and remain the whole life. It does not represent a serious danger for health and it is not contagious, but it is painful for the person that is affected by it.