In the skin, immediate hypersensitivity can result in skin eruptions or urticaria, characterized by wheals with redness.
Atopic dermatitis, which affects a small number of infants, is one of several genetically linked disorders that include asthma, hay fever, and urticaria.
Whealing reactions (hives, nettle rash, urticaria) constitute a special form of inflammation in which vascular changes predominate, with little or no inflammatory cellular reaction.
Since histamine is an important causative agent in urticaria, most cases respond to antihistamine treatment.
Though the 20-year-old's failure to arrive for the second half in temperatures of -6C raised scorn in some quarters, with the former City defender and BBC summariser Danny Mills among those unimpressed, Balotelli has experienced several mild forms of the same allergic urticaria during his seven-month City career and two similar incidents caused him serious alarm while at Internazionale.
Symptoms vary with the drug and the sensitivity of the affected person but include, as separate reactions, hives (urticaria), serum sickness, and, rarely, anaphylaxis (collapse of the circulatory system with accompanying respiratory symptoms).
Several specific causes of hives, as well as variant forms of its typical skin lesions, are denoted by qualifying the term urticaria with a descriptive word.
The mechanism by which psychogenic factors give rise to chronic urticaria is not clear, but the overall sequence of biological events that triggers acute urticaria has been clarified.
Allergy to a specific food is probably the most frequent cause of acute urticaria; fish, eggs, berries, and nuts head the list of common offenders.
Emotional and mental stresses are believed to be major and contributing causes of chronic urticaria.
Complications of chronic urticaria and a related condition, angioedema, may include lethal breathing difficulties and anaphylactic shock.
