common condition

usually non-allergenic

majority; no cause found

symptom relief: oral non-sedating antihistamine = first-line

most acute; some episdoes several months/years

Classification/aetiology

• group of skin conditions

  • presence of wheals

• 1/5 experience urticaria at some stage in life

• many cases specific trigger for urticaria not found

• two main tyeps;

  • 1. ordinary (spontaneous)

       1. acute

       2. chronic

    2. Physical urticare

Acute urticara

• one-off outbreaks/recurrent episodes

• occur period \<6/52

• most common

• children/young adults

• 20-30% cases develop into chronic urticaria

• approx 50% idiopathic

Chronic urticaria

• episodes over period longer than 6/52

• may persist for lifetime

• -more common physical

• 30% of patients in primary care with urticaria have chronic urticaria

• mroe common in adults

• 40% have evidence of autoimmune process

  • 20% evidence of physical stimulus

Physical urticaria

• localised area after contact with physical stimulus

• resolve within 2 hours period

  • chronic recurring condition

• dermatographism is most common form

• other types:

  • contact urticaria

  • cholinergic urticaria - sweating

  • Delayed pressure urticaria

  • Cold urticaria

  • solar urticaria

  • vibratory urticaria

Non-allergenic:

most cases of urticaria are not caused by allergy but result of histamine being released by direct mast cell degranulation (non igE mediated)

• infection

  • bacterial: helicobacter, mycoplasma

  • viral: infectious mon, viral hep

  • parasitic; giardia

  • fungal; candidia

• Medicines; especially opiates, aspirin, nsaids

• non-allergecnic contact with topical compounds, food preservatives, raw meat or vege

• non allergenic food reactions to compounds; etoh, salicylates inf ruit, bacterial decomposition

• hypersensitivity to phsyical stimuli

• autoimmune; SLE, autoimmune thyroid

Allergenic

most common in people with history of atopy

• medicines - abx

• food allergy

• insect stings

• contact allergens

clinical hsitory

• lesions; determine type of urticaria

  • frequency,

  • size,

  • distribution,

  • duration

• triggers;

  • recent consumptoin of new/unsuual substance/new activity

• occupational history

• history of simialr epsiodes, and response to treatment

• personal/family hsitory of atopy

physical exam

• highly pruritic, well defined, pink/red wheals often with pale centre

• usually last \<48hours anad leave no remaining marks

• occur anywhere on skin

• vary in shape

  • ring,

  • wavy, serpiginous

  • gyrate, circular/coiled

  • taretoid, target

  • merge to form geographic /giant patches

  • surface remains smooth

• 40% have sign of angioedema

  • involves deeper epidermis and subcut tissues

  • frequnetly affects

    • eyes

    • mouth

    • throat

    • tongue

    • hands

    • feet

differential diagnosis

• Atopic dermatitis

  • lack of transitory wheals

  • dry skin

  • other skin surface abN

• Contact dermatitis

  • lack of transitory wheals

  • presence of skin surface changes

    • blisters

    • dryness

    • peeling

  • fixed drug eruptions

    • tender

    • well defined

    • round/oval patches

    • generallly same place on body

  • erythema multiforme

    • acute/recurring hypersensitivity

    • lesions usually present on face and distal limbs

    • last up to 7 days

  • bullous pemphigoid

    • chronic autoimmune condiiton

    • elderly

    • eroisions and tense bullar dilled with clear cloudy blood stained

  • urticarilal vasculitis

  • papular urticaria

investigations

• not generally required

• may be useful selected patients with chronic urticaria

• skin prick testing may be considered when allergic cause suspected

Treatment

• actue generally resolves over short period

• chronic can persist for months/years

• 47% symptom free

• 16% with physical were symptom free

• 60% with ordinary urticaria and angioedema

• Avoidance

• Pharmacological:

  • commence non-sedating oral antihistamine

    • 10mg od/bd

    • cna go up to 40mg daily

  • add conventional sedating/H2 antagoinsit

  • add TCA

    • doxepin

  • add oral corticosteroids

  • Topical corticosteroids not helpful

    • may cause adverse effects with long-term/higher potency

  • cooling preparations

  • PUVB reduces mast cells in upper dermis

• uncommon during pregnancy

• all antihistamines should be avoided during pregnancy

• no reports of major birth abnormal using newer nonsedating antihistmines