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Similar clinical pictures. It is actually fairly difficult to confuse urticaria with other diseases. This reflects the highly characteristic skin manifestations associated with urticaria: the wheal and flare type skin reaction and the swelling of the skin's deep tissue. These manifestations are also transient, i.e. only last for a brief period (wheals: minutes to a few hours, angioedema: hours to a few days). Wheals and angioedema heal without leaving visible traces on the skin. There are neither scars nor scabs, nor haemorrhaging. This clearly differentiates urticaria from most other skin diseases. In other words: if the characteristic itchiness appears together with the wheals and/or the swelling, then the diagnosis of urticaria is an easy one.

Urticaria is related to so-called Hereditary AngioEdema (HAE), a rare disease that often afflicts several members of a family. This too involves swelling of the skin, particularly in the face. That is about the only thing that HAE and urticaria have in common, however. HAE develops differently, has other causes, requires different treatment, and is most clearly distinguished from urticaria by the fact that it involves neither wheals nor itchiness.

Also worth mentioning is urticaria vascultitis, sometimes described as the "big brother" of hives. This significantly more rare disease is characterized by wheals that remain for more than a day and which leave behind discolouration of the skin even after they have healed.

Urticaria as a concomitant disease.  Urticaria is more of a reaction pattern than a discrete skin disease. It should therefore not come as a surprise that urticarial episodes appear within the framework of many of other clinical pictures. Here too, the spectrum is very broad: wheals and itchiness appear when we are bothered by mosquitoes; wheals and itchiness can also appear during a (sometimes fatal) anaphylactic shock (see below).

Diseases in connection with urticaria. This group includes diseases that are viewed as potential causes of urticaria: urticaria sufferers are frequently affected by a special form of thyroid infection (through what are known as autoantibodies). On the other hand, certain diseases appear more frequently in patients with chronic urticaria that nevertheless cannot (yet) be made responsible for the appearance of urticaria, such as vitiligo, spot baldness (Alopecia areata) and diabetes.

Complications from urticaria. Given how frequently urticaria occurs, complications are very rare and tend to be restricted to the following two exceptions:

• urticaria as part of an anaphylactic or allergic shock
• appearance of angioedema in the face and/or throat

For an anaphylactic shock – which results when a bee stings someone allergic to bee venom, for example – urticaria is one of many symptoms, and hardly the most threatening. Depending on the extent of the anaphylactic reaction, symptoms may range from malaise, vomiting, diarrhoea and poor circulation to unconsciousness and apnoea or cardiac arrest. Strictly speaking, the anaphylactic shock is not a complication of urticaria, but rather urticaria is a component of the anaphylactic shock.

Angioedema in the face and throat are another matter if they occur as part of urticaria. This can involve swelling of the tongue and larynx, for example, which in turn can lead to a misshaping of the airways and then acute dyspnoea (shortness of breath). In either case, it is a good idea to keep around an emergency kit, i.e. quick acting drugs in fluid form.

There are also a series of physical symptoms that can occur alongside an urticarial episode, but which are not necessarily seen as a complication of urticaria: malaise, abnormal fatigue, diarrhoea, headaches and joint pain.