Urticaria caused by direct heat

This is a process that is not very frequent on which localized heat produces pruritus and the emergence of hives in the area of contact. The mechanism of production is unknown although in some patients (not in all of them of course) it has been proven an increment of histamine in plasma after the provocation with heat. In some cases it has been recognized in a delayed and familiar form; that this condition responds to anti-H1 and atropine.

This condition is very common among men. One of the triggers of the emergence of hives of heat urticaria is the sudden change of temperature, when the person changes of environment and is exposed to a change of environmental temperature, these changes can lead to the person to urticaria attacks. The persons affected by this type of allergy should avoid demanding physical exercise routines, sauna baths and spicy foods. The symptoms presented by this condition may include:

• Rounded spots or hives on the body
• Raised hives on skin
• Reddish hives with itching which can emerge in groups
• The minimum size of these hives is of about three millimeters of diameter
• They can also affect internal areas like throat, and extremities like legs and arms, it can also affect the area of the thorax
• The inflammation with angioedema can also affect lips, face and tongue
• Hives emerge suddenly

Around sixteen percent of population is affected at least once in their lives by the emergence of urticaria hives caused by heat. There are mainly two types of urticaria. One of them is acute urticaria on which case the eruptions last less than six weeks and the other type is chronic urticaria, on which hives can last more than six weeks. In the case of chronic urticaria is very difficult to identify the cause unlike the case of acute urticaria.

Clinical manifestations

Clinical manifestations consist on the emergence of erythema, pruritus, edema and hives after just a few minutes subsequent to the application of local heat (thirty eight to fifty six Celsius degrees) originated on any source like hot water, contact with hot objects (such as coffee cups, or the seat of a car during the summer), irradiation of sunlight or of an artificial source. Lesions are localized only con the cutaneous area that is exposed to heat and they can remit after one hour.

The clinical case can be accompanied by systemic symptoms like headaches, wheezing, abdominal pain and syncope. After an episode there is a refractory period which can last many weeks (the time that takes to a mast cell to reload its content of histamine). There has been described a familiar delayed form which appears two hours after the exposition it heat and it can persist for twelve or fourteen hours. This condition can be associated to urticaria produced by cold.

Diagnosis

It can be done by applying a metallic cylinder of hot water during five minutes to the skin.