1.2 Urtica

Wheal, hive.

Wheal: localized transient flattened sub-epidermal edema with initial complete later peripheral erythema; can be red or pale pink.

Angioedema: localized edema in the deeper dermis, less sharply defined, firm but compressible swelling.

Urticaria: usually associated with marked pruritus (itching).

Angioedema: feeling of pressure, if on mucous membranes sensation of stricture.

Urticaria: can appear anywhere on body, especially on trunk and extremities, less often on face and scalp.

Deep seated wheals are localized in the  subcutaneous fat.

Angioedema: most common on cheeks, eyelids, lips, oral and genital mucosa.

Transient, lesions change over minutes to hours, finally annular figurated flattening.

Associated with macules, erythema and flushing.

Resolves completely without scarring or other changes.

An individual hive typically never lasts more than 24 hours, although a case of hives may last days to weeks. Other diseases may cause persistent urticated lesions (vasculitis, lupus erythematosus).

Usually intense pruritus.

Many causes: physical factors, infections, allergic reactions, medications, mastocytosis.

Angioedema: deep edema after the lower dermis (pale, firm swelling).

Acute, spontaneous urticaria, chronic urticaria, urticarial exanthema of other reasons.

Angioedema.

Mast cells, basophils; release histamine and other inflammatory mediators (prostaglandins, leukotrienes).

Triple response to histamine: pruritus, macular erythema, hive.