Itchy skin disease
Urticaria key points test
Which of the following statements are true?
# Urticarial weals often persist longer than 24 hours
# Weals in physical urticaria persist longer than 24 hours
#! Weals may be asymptomatic
#! Angioedema may be due to decreased C1
Explanation: Urticaria by definition causes asymptomatic or pruritic weals that have typically changed or cleared within 24 hours. Brief weals lasting 15-60 minutes are characteristic of physical urticaria. Angioedema is the name given to deeper cutaneous swelling and is sometimes caused by deficiency of C1 inhibitor.
Chronic urticaria is sometimes due to:
# IgE-mediated Type 1 hypersensitivity reaction to shellfish
#! Anti-FceRI autoantibodies
#! Opiate dependence
Explanation: Chronic urticaria is defined as regular wealing that persists for more than 6 weeks and is a reaction pattern resulting from mast cell degranulation. If no explanation is found, the urticaria is said to be idiopathic but in about 25-50% of cases it is now known to be due to autoimmune disease. Autoantibodies have been demonstrated to high affinity immunglobulin E receptors (anti-FceRI). Drugs such as opioids and aspirin and foods and food additives such as strawberries and tartrazine, may be under-recognized as causes of chronic urticaria through nonimmunological degranulation of mast cells. It may also be associated with systemic lupus and other systemic autoimmune diseases. Chronic urticaria is treated with nonsedating antihistamines such as cetirizine.
Acute urticaria is sometimes due to:
#! IgE-mediated Type 1 hypersensitivity reaction to shellfish
# Anti-FceRI autoantibodies
#! Opiate dependence
Explanation: Acute urticaria is more common in children than in adults and is one the most common reasons to present to an emergency department. It may persist from a few hours to several weeks (when it merges with chronic urticaria). Histamine release can be immune-mediated (type 1 allergic IgE response or type 3 immune complex disease) or nonimmune-mediated due to drugs, foods and food additives. In about 40% of cases it is caused by a recent viral illness.
Which of the following may cause physical urticaria:
#! Stroking the skin
#! Prolonged pressure on the skin
#! Direct application of heat to the skin
#! Application of an ice-block to the skin
Explanation: Physical urticaria results from stroking the skin (dermographism), sweating (cholinergic urticaria), prolonged pressure (delayed pressure urticaria), direct application of heat (heat urticaria), sun exposure (solar urticaria), and exposure to cold (cold urticaria)
Contact urticaria may be caused by:
#! Allergens such as latex in rubber gloves
#! Irritants such as sorbic acid in hand cream
# Corticosteroid injections
Explanation: Contact urticaria may be immunological, non-immunological or unclassified in origin. Urticaria appears within minutes to an hour after exposure to the causative agent and generally recovers quickly. However, eczema may follow over the next few days. Type I hypersensitivity reactions may be due to contact with latex and may progress to generalized urticaria and anaphylaxis. Non immunological causes include various fragrances and other components of cosmetics and plants such as nettles.
Which of the following antihistamines is most likely to cause sedation?
Explanation: Loratidine, cetirizine and fexofenadine are classifed as nonsedating antihistamines, although mild sedation may arise in some individuals. Promethazine is often used to help itchy patients sleep more soundly because of its sedative properties.