Urticaria is a skin symptom that accompanies many allergic disorders . It is a relatively common disorder caused by localized mast-cell degranulation, with resultant dermal venular hyperpermeability culminating in pruritic wheals. Mostly results from an antigen-induced ( pollens , foods , drugs , insect venom ) release of histamine and other vasoactive amines via sensitization with specific IgE antibodies. Most individual lesions develop and fade within 24 hours.
Allergic skin diseases such as urticaria and angioedema as well as atopic dermatitis are not clearly defined as true allergic diseases. Urticaria and angioedema are both due to excessive mast cell activity in the skin. Chronic urticaria and angioedema are seldom due to a definable IgE mechanism (as is the case with all allergies) but, when determined, is generally due to a drug , food or food additive.

Classification of Urticaria

Acute Urticaria and Urticaria with an Identifiable Cause  Chronic Idiopathic Urticaria  Physical Urticaria  Aquagenic Urticaria  Cholinergic Urticaria  Cold-Induced Urticaria (cold urticaria)   Dermographism (symptomatic dermographism)  Delayed Pressure Urticaria  Exercise-Induced Anaphylaxis

Localized Heat Urticaria  Solar Urticaria  Vibratory Urticaria  Angioedema  Others  Hereditary urticaria  Contact urticaria  Papular urticaria  Urticarial vasculitis  Urticaria pigmentosa

Atopic dermatitis is associated with high serum IgE levels as well as a history of atopic disease ( rhinitis , asthma , etc.). Unfortunately, management is difficult since the medications classically associated with treatment of allergic diseases (i.e. antihistamines ) have little effect in these patients.

Dermatographism
A common form of hives is dermatographism, which occurs in 5% of the population. The hives are caused by a constant stroking or rubbing of the skin and often occur following scratching, or when tight-fitting clothes rub the skin.

  Drugs
  Foods
 Inhalants, for example: pollens , mould , house dust mites
  Drugs
  Drugs