Urticaria

The hives (urticaria) is a pathological skin reaction to food or drugs ( allergies), on effects of heat or cold, light, pressure or water on immunological phenomena or to mental stress. Features include hives or erythema. Acute urticaria is - in contrast to chronic - not more than six weeks; often a trigger can not be determined (idiopathic urticaria).

Overview

The disease starts with first pale red to red elevations of the skin, similar to mosquito bites. The changes are larger, form hives or itchy erythema and - similar to the reaction in contact with stinging nettles (Urtica ), hence the name. The wheals may have a few millimeters in diameter or as large as the entire palm. In disseminated urticaria large parts of the body surface can be affected. Around the wheals often forms a reddish Reflexerythem. Occasionally, the rash is not continuous at a certain point, but it travels through the body. The rash then changes its position within a short time and the place of origin is nothing more to see it. The recovery usually takes 3 to 4 hours maximum after 12 hours is usually no longer visible appearance.

Wheals are edematous elevations of the dermis of a pale red color ( urticaria rubra), the skin color with pronounced edema or pale - white ( urticaria porcellanea ) may appear. Cause of the swelling is usually the release of the neurotransmitter histamine from mast cells, which increases the permeability of the dermal blood vessels and thus leads to water retention in the dermis. The reasons for the release of this substance are different, however, in only 10% of all cases the cause of allergy. Rather, there are a large number of causes and underlying causes; usually there are the following options:

• Autoreactivity ( endogenous substances are not tolerated; see autoimmune diseases )
• Hypersensitivity to drugs or food additives ( preservatives, colorings and flavorings )
• Chronic infections that can run free of symptoms until the urticaria (eg in the digestive tract)
• Histamine degradation disorder that causes increased histamine release from the mast cells

This can eventually lead to the formation of angioedema; Swelling of the face regions in the oral and pharyngeal mucosa and the larynx can lead to life-threatening respiratory distress.

Chronic urticaria may also have organic causes, such as disturbances in the adrenal cortex or hidden foci of inflammation in the body.

A bacterium in the stomach, Helicobacter pylori, may be the cause of hives. Other bacterial infections as triggers of hives are known.

Stress can increase the urticaria, but is also discussed as a trigger.

Physical urticaria

Physical urticaria are not triggered by chemical substances, but by external application of pressure, heat or cold. They belong to the pseudo-allergies, so there are no allergy in the medical sense. Probably due to a dysregulation of histaminergic system causes the stimulus, the release of histamine, an endogenous mediator substance, which in turn triggers the symptoms.

The individual forms are urticaria factitia or urticarial dermographism ( wheals in the pattern of a mechanical action such as by scratching or pressing, painting or writing on the skin), Urticaria, Sonnenurtikaria, Vibrationsurtikaria and the relatively frequent cold urticaria - also commonly referred to as " cold allergy".

Contact with (sun ) light triggers some forms of metabolic disorder Erythropoietic protoporphyria (EPP) an urticaria -like reaction from (EPP from urticaria - type).

Other forms

Rare forms are triggered by psychological stimuli cholinergic and adrenergic urticaria, where the designations express that activation of the autonomic nervous system plays a role. Another form is the extremely rare Aquagenic urticaria, are triggered when the itchy hives and rash even when in contact with distilled water. There are only a few case reports in the literature. The mechanism of this disorder is still unknown; Speculation suggests that soluble substances of the skin are flooded with the water in the pores. As with the physical triggers, it is also incorrect to speak of an allergy or even " water allergy".

Treatment options

Often the symptoms disappear within a few hours, usually just as quickly as they appeared. Then, no treatment is necessary. However, care should be taken to avoid the possible triggers.

If it lasts longer, the doctor may administer antihistamines or cortisone to suppress the symptoms. In chronic urticaria, the treatment can also be done over a longer period, however, should always be inserted treatment interruptions to control whether the hives has regressed spontaneously.

If persistent chronic hives can make a multi-day hospital stay necessary to find the triggers under certain circumstances.

A published in March 2013 study by the Allergy Research Group of the Charité in Berlin showed that in previously unsuccessfully treated with antihistamines patient's asthma drug omalizumab represents a successful treatment option.

Pictures

Wheals

Detail

Mechanical irritation