Types of physical urticaria

Physical urticaria manifestations are characterized for the emergence of hives after a specific physical stimulus. It happens on about fifty percent of patients affected by chronic urticaria and a patient can be affected for more than one type of physical urticaria at the same time, like dermographism and cholinergic urticaria as an example. Physical urticaria manifestations can coexist with ordinary urticaria. It is important to confirm the diagnosis with physical tests; there are general guides of consensus for these tests. Physical urticaria can be divided in a variety of types.

Dermographism, delayed urticaria for pressure and vibratory angioedema

These manifestations can be caused by a mechanical trauma like friction (a scrape or a scratch), pressure (tight clothes) and vibration respectively. The symptomatic dermographism can be produced with the emergence of a pruritic linear hive five or ten minutes after receiving the stimulus on skin. This condition can happen at any age and remain for two or three years but the time of duration can extend even more. Reactions can emerge on places where there is a friction of skin with clothes and the pruritus can be severe. The mucous compromise and angioedema do not take place.

The delayed urticaria for pressure happens two or six hours after a maintained perpendicular pressure over the skin. Hives are pruritic, painful, and hot and in contrast with other types of physical urticaria types, on which the life of hives is short (less than an hour), they can last for even twenty four hours. Tight dresses and clothes are usually the most frequent trigger. This condition can be associated to a slight pyrexia and arthralgia. There have been reported cases of anaphylaxis after tests of pressure and large areas that are compromised can look very similar to an angioedema. The cause is unknown.

The vibratory angioedema is a non frequent type, where hives have a very short lifetime and are caused by vibration, like for instance placing the hands on the wheel of a lawnmower or by a strong handshake.

Cholinergic urticaria

It is present with multiple hives of two to three millimeters of diameter which are extended from neck to thighs, although any region of the body can be compromised by this condition. It mainly affects to teenagers and young adults. It is caused by an increment on the body temperature (in about 0.7 to 1 Celsius degrees) due to exercise, hot water showers, tube baths, emotions or stressing situations and also for febrile cases and the intake of spicy or hot food.

 The cholinergic sympathetic innervations of sweating glands are compromised but the mechanism that takes place is ignored. The anaphylaxis induced by exercise can look similar to a cholinergic urticaria in some cases; the syndrome is characterized for pruritus, hives and angioedema which can progress until producing a breathing obstruction or cardiovascular collapse. It has been related to the intake of specific foods or the excessive ingest of food before exercise routines. It affects thorax and neck.