Description

• A cutaneous lesion or lesions involving edema of the epidermis and/or dermis presenting with rapid onset and pruritus, returning to normal skin appearance within 24 hours
• Pathophysiology is primarily mast cell degranulation and subsequent histamine release.
• Angioedema may occur with urticaria, which is characterized by sudden pronounced erythematous nonpitting edema of the lower dermis and subcutis; may take up to 72 hours to remit
• Pruritus and burning are more commonly associated with urticaria; pain more often with angioedema
• Lesions can occur on any part of the body.
• Urticaria can be classified as acute or chronic.
  • Acute: if lesions recur within <6 weeks
  • Chronic: recurring lesions that persist for >6 weeks
• Three main causal categories of urticarial lesions
  • Immunoglobulin E (IgE) mediated
  • Non-IgE immunologically mediated
  • Nonimmunologically mediated
• Underlying etiology may be difficult to pinpoint, although in some cases possible.
• For those with chronic urticaria, 40% have concurrent angioedema
• Etiology of urticaria is either spontaneous or induced.
• System(s) affected: integumentary
• Synonym(s): hives; wheals

Epidemiology

Incidence

• Equally distributed across all ages: female > male (2:1 in chronic urticaria)
• In 20% of patients, chronic urticaria lasts >10 years.

Prevalence

• 5–25% of the population
• Of people with urticaria, 40% have no angioedema, 40% have urticaria and angioedema, and 20% have angioedema with no urticaria.
• Up to 3% of the population has chronic idiopathic urticaria.

Etiology and Pathophysiology

• Mast cell degranulation with release of inflammatory reactants, which leads to vascular leakage, inflammatory cell extravasation, and dermal (angioedema) and/or epidermal (wheals/hives) edema
• Histamine, cytokines, leukotrienes, and proteases are main active substances released.
• If release of histamine and other mediators occurs in the dermis, urticaria lesions result. If release occurs deep in the dermis, then angioedema develops.
• Acute spontaneous urticaria (ASU)
  • Bacterial infections: strep throat, sinusitis, otitis, urinary tract
  • Viral infections: rhinovirus, rotavirus, hepatitis B, mononucleosis, herpes
  • Foods: peanuts, tree nuts, seafood, milk, soy, fish, wheat, and eggs; tend to be IgE-mediated; pseudoallergenic foods such as strawberries, tomatoes, preservatives, and coloring agents contain histamine.
  • Drugs: IgE-mediated (e.g., penicillin and other antibiotics), direct mast cell stimulation (e.g., aspirin, NSAIDs, opiates)
  • Inhalant, contact, ingestion, or occupational exposure (e.g., latex, cosmetics)
  • Parasitic infection; insect bite/sting
  • Transfusion reaction
• Chronic spontaneous urticaria (CSU)
  • Chronic subclinical allergic rhinitis, eczema, and other atopic disorders
  • Chronic indolent infections: Helicobacter pylori, fungal, parasitic (Anisakis simplex, strongyloidiasis), and chronic viral infections (hepatitis)
  • Collagen vascular disease (cutaneous vasculitis, serum sickness, lupus)
  • Thyroid autoimmunity, especially Hashimoto
  • Hormonal: pregnancy and progesterone
  • Autoimmune antibodies to the IgE receptor α chain on mast cells and to the IgE antibody
  • Chronic medications (e.g., NSAIDs, hormones, ACE inhibitors). NSAID sensitivity demonstrated almost in half of adults with chronic urticaria and presents with a worsening of symptoms 4 hours after ingestion.
  • Malignancy
  • Physical stimuli (cold, heat, vibration, pressure) in physical urticaria
• Chronic inducible urticaria (CIU)
  • Dermatographism: “skin writing” or the appearance of linear wheals at the site of any type of irritation. This is the most common physical induced urticaria.
  • Cold urticaria: Wheals occur within minutes of rewarming after cold exposure; 95% idiopathic but can be due to infections (mononucleosis, HIV), neoplasia, or autoimmune diseases.
  • Delayed pressure urticaria: Urticaria occurs 0.5 to 12 hours after pressure to skin (e.g., from elastic or shoes), may be pruritic and/or painful, and may not subside for several days.
  • Solar urticaria: from sunlight exposure, usually UV; onset in minutes; subsides within 2 hours
  • Heat urticaria: from direct contact with warm objects or air; rare
  • Vibratory urticaria/angioedema: very rare; secondary to vibrations (e.g., motorcycle)
  • Cholinergic urticaria: due to brief increase of core body temperature from exercise, baths, or emotional stress. This is the second most common induced urticaria.
  • Adrenergic urticaria: caused by stress; extremely rare; vasoconstricted, blanched skin around pink wheals as opposed to cholinergic’s erythematous surrounding
  • Contact urticaria: wheals at sites where chemical substances contact the skin, may be either IgE-dependent (e.g., latex) or IgE-independent (e.g., stinging nettle)
  • Aquagenic and solar urticaria: small wheals after contact with water of any temperature or UV light, respectively; rare

Genetics
No consistent pattern known: Chronic urticaria has increased frequency of HLA-DR4 and HLA-D8Q MHC II alleles.

General Prevention

Avoidance of known triggers is the mainstay of prevention.

Commonly Associated Conditions

• Angioedema (common)
• Anaphylaxis (somewhat common)