eMedicine Specialties > Emergency Medicine > Dermatology

Urticaria

Author: M Scott Linscott, MD, FACEP, Professor, Division of Emergency Medicine, Professor of Surgery (Clinical), University of Utah School of Medicine
Contributor Information and Disclosures

Updated: Jul 6, 2009

Introduction

Background

Urticaria, commonly referred to as hives, is the most frequent dermatologic disorder seen in the ED. It appears as raised, well-circumscribed areas of erythema and edema involving the dermis and epidermis that are very pruritic. Urticaria may be acute (lasting less than 6 wk) or chronic (lasting more than 6 wk). A large variety of urticaria variants exist, including acute immunoglobulin E (IgE)–mediated urticaria, chemical-induced urticaria (non-IgE-mediated), urticarial vasculitis, autoimmune urticaria, cholinergic urticaria, cold urticaria, mastocytosis, Muckle-Wells syndrome, and many others.¹

Acute IgE-mediated urticaria is the most benign form of anaphylaxis. It usually occurs independently, but it may be accompanied by the more serious clinical manifestations of anaphylaxis, angioedema, and anaphylactic shock. The etiology of both acute and chronic urticaria are numerous (see Causes below). The etiologic agent is more likely to be identified in acute urticaria (40-60%) than in chronic urticaria (10-20%). The lesions of IgE-mediated urticaria usually last less than 24 hours and are often migratory, leaving no residual skin abnormalities. The lesions of urticarial vasculitis usually last longer than 24 hours, are both painful and pruritic, and often leave purpuric and hyperpigmented lesions.^2,3

For more information, see Medscape's Allergy Resource Center.

Pathophysiology

Urticaria results from the release of histamine, bradykinin, leukotriene C4, prostaglandin D2, and other vasoactive substances from mast cells and basophils in the dermis. These substances cause extravasation of fluid into the dermis, leading to the urticarial lesion. The intense pruritus of urticaria is a result of histamine released into the dermis. Histamine is the ligand for 2 membrane-bound receptors, the H1 and H2 receptors that are present on many cell types. The activation of the H1 histamine receptors on endothelial and smooth muscle cells leads to increased capillary permeability. The activation of the H2 histamine receptors leads to arteriolar and venule vasodilation.⁴

This process is caused by several mechanisms. The type I allergic IgE response is initiated by antigen-mediated IgE immune complexes that bind and cross-link Fc receptors on the surface of mast cells and basophils, thus causing degranulation with histamine release. The type II allergic response is mediated by cytotoxic T cells, causing deposits of immunoglobulins, complement, and fibrin around blood vessels. This leads to urticarial vasculitis. The type III immune-complex disease is associated with systemic lupus erythematosus and other autoimmune diseases that cause urticaria.⁴

Complement-mediated urticarias include viral and bacterial infections, serum sickness, and transfusion reactions. Urticarial transfusion reactions occur when allergenic substances in the plasma of the donated blood product react with preexisting IgE antibodies in the recipient. Certain drugs (opioids, vecuronium, succinylcholine, vancomycin, and others) as well as radiocontrast agents cause urticaria due to mast cell degranulation through a non-IgE mediated mechanism. The physical urticarias in which some physical stimulus causes urticaria include immediate pressure urticaria, delayed pressure urticaria, cold urticaria, and cholinergic urticaria. Finally, there are urticarias, especially chronic urticarias, for which no cause can be found, despite exhaustive efforts—the so-called idiopathic urticarias.⁴

Frequency

United States

Urticaria affects 15-20% of the general population at some time during their lifetime.

International

The frequency of urticaria internationally is similar to that in the United States.

Mortality/Morbidity

Pruritus (itching) and rash are the primary manifestations of urticaria, and hyperpigmentation or hypopigmentation are rare. Acute urticaria is usually self-limited and commonly resolves within 24 hours but may last up to 6 weeks. Chronic urticaria lasts more than 6 weeks. Neither acute nor chronic urticaria results in long-term consequences other than anxiety and depression. The depression can be severe enough to lead to suicide in rare cases. Also, many of the diseases associated with chronic urticaria may cause very significant morbidity and mortality.

Race

No variation in race is noted.

Sex

Incidence rates for acute urticaria are similar for men and women; chronic urticaria occurs more frequently in women (60%).

Age

Urticaria can occur in any age group, although chronic urticaria is more common in the fourth and fifth decades.

Clinical

History

Information regarding history of previous urticaria and duration of rash and itching is useful for categorizing urticaria as acute, recurrent, or chronic.

• For chronic or recurrent urticaria, important considerations include previous causative factors and the effectiveness of various treatments.^5,6
• Ask about precipitants, such as heat, cold, pressure, exercise, sunlight, emotional stress, or chronic medical conditions (eg, hyperthyroidism, systemic lupus erythematosus [SLE], rheumatoid arthritis, polymyositis, amyloidosis, polycythemia vera, lymphoma and other malignant neoplasms).
• Ask about other medical conditions that can cause pruritus (usually without rash), such as diabetes mellitus, chronic renal insufficiency, primary biliary cirrhosis, or other nonurticarial dermatologic disorders (eg, eczema, contact dermatitis).
• Ask about family and personal medical history of angioedema, which is urticaria of the deeper tissues and can be life threatening if it involves the larynx and vocal cords. Causes specific to angioedema include hereditary angioedema (a deficiency in C1-inhibitors) and acquired angioedema (associated with angiotensin-converting enzyme [ACE] inhibitors and angiotensin receptor blockers (ARBs). Characteristics of angioedema include the following: 
  • Vasodilation and exudation of plasma into deeper tissues than is seen in simple urticaria
  • Swelling that is generally nonpitting and nonpruritic and usually occurs on the mucosal surfaces of the respiratory tract (lips, tongue, uvula, soft palate, and larynx) and GI tract (swelling of the intestine leading to severe abdominal pain)
  • Hoarseness, the earliest sign of laryngeal edema (Ask the patient if he or she has had a voice change.)
• For acute urticaria, ask about possible precipitants, such as the following⁷ : 
  • Recent illness (eg, fever, sore throat, cough, rhinorrhea, vomiting, diarrhea, headache)
  • Medication use including penicillins, cephalosporins, sulfas, diuretics, aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), iodides, bromides, quinidine, chloroquine, vancomycin, isoniazid, antiepileptic agents, and other agents.
  • Intravenous radiocontrast media
  • Travel (amebiasis, ascariasis, strongyloidiasis, trichinosis, malaria)
  • Foods (eg, shellfish, fish, eggs, cheese, chocolate, nuts, berries, tomatoes)
  • New perfumes, hair dyes, detergents, lotions, creams, or clothes
  • Exposure to new pets (dander), dust, mold, chemicals, or plants
  • Pregnancy (usually occurs in last trimester and typically resolves spontaneously soon after delivery)
  • Contact with nickel (eg, jewelry, jeans stud buttons), rubber (eg, gloves, elastic bands), latex, industrial chemicals, and nail polish
  • Sun or cold exposure
  • Exercise

Physical

Urticaria is characterized by blanching, raised, palpable wheals, which can be linear, annular (circular), or arcuate (serpiginous). These lesions occur on any skin area and are usually transient and migratory.

• Dermographism may occur (urticarial lesions resulting from light scratching).
• The physical examination should focus on conditions that might precipitate urticaria or could be potentially life threatening.⁷   
  • Pharyngitis or upper respiratory infections, particularly in children
  • Angioedema of the lips, tongue, or larynx 
  • Scleral icterus, hepatic enlargement, or tenderness that suggests hepatitis or cholestatic liver disease
  • Thyromegaly suggesting autoimmune thyroid disease 
  • Lymphadenopathy or splenomegaly that suggests lymphoma
  • Joint examination for any evidence of connective tissue disease, rheumatoid arthritis, or systemic lupus erythematosus (SLE)
  • Lungs for pneumonia or bronchospasm (asthma)
  • Extremities for evidence of bacterial or fungal infection

Causes

• The cause of acute generalized urticaria often is undetermined (some sources report that the cause is undetermined in more than 60% of cases). Known causes include the following:
  • Infections (eg, pharyngitis, GI infections, genitourinary infections, respiratory infections, fungal infections [eg, dermatophytosis], malaria, amebiasis, hepatitis, mononucleosis, coxsackievirus, mycoplasmal infections, infestations [eg, scabies], HIV, parasitic infections [eg, ascariasis, strongyloidiasis, schistosomiasis, trichinosis])
  • Foods (particularly shellfish, fish, eggs, cheese, chocolate, nuts, berries, tomatoes)
  • Drugs (eg, penicillins, sulfonamides, salicylates, NSAIDs, codeine, antihistamines)
  • Environmental factors (eg, pollens, chemicals, plants, danders, dust, mold)
  • Exposure to latex
  • Exposure to undue skin pressure, cold, or heat
  • Emotional stress
  • Exercise
  • Pregnancy (ie, pruritic urticarial papules and plaques of pregnancy [PUPPP])
• Chronic urticaria can be related to all of the above as well as to the following:
  • Autoimmune disorders (SLE, rheumatoid arthritis, polymyositis, thyroid autoimmunity, and other connective tissue diseases); probably up to 50% of chronic urticaria is autoimmune.⁶
  • Cholinergic urticaria induced by emotional stress, heat, or exercise (Examine for other signs of cholinergic stimulation including lacrimation, salivation, and diarrhea.)
  • Chronic medical illness, such as hyperthyroidism, amyloidosis, polycythemia vera, malignant neoplasms, and lymphoma
  • Cold urticaria, cryoglobulinemia, cryofibrinogenemia, or syphilis
  • Mastocytosis
  • Muckle-Wells syndrome
  • Familial cold autoinflammatory syndrome
• The etiology of chronic urticaria is undetermined in at least 80-90% of patients.
• Urticaria pigmentosa is a familial dermatologic disorder characterized by hyperpigmented (yellow, tan, or brown) papules or plaques that may be associated with lymphoproliferative disorders. These lesions are composed of mast cells. When the skin overlying an individual lesion of urticaria pigmentosa is stroked, a linear wheal is formed; this characteristic and diagnostic sign is known as the Darier sign.
• Recurrent urticaria can be related to the following:
  • Sun exposure (solar urticaria, occurring only on skin exposed to the sun)⁸
  • Exercise (cholinergic urticaria)
  • Emotional or physical stress
  • Water (aquagenic urticaria)

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