What is the difference between Urticaria and Anaphylaxis?

From the Guidelines

Urticaria and anaphylaxis are distinct allergic reactions with different levels of severity, and anaphylaxis is a life-threatening condition that requires immediate epinephrine administration, whereas urticaria can typically be managed with antihistamines. The key difference between the two conditions lies in the involvement of other organ systems beyond the skin and the potential for rapid progression to shock and airway compromise in anaphylaxis 1. Urticaria, commonly known as hives, is characterized by raised, itchy welts on the skin that can appear and disappear quickly, and it's typically limited to the skin and rarely life-threatening. Anaphylaxis, on the other hand, is a severe, potentially life-threatening systemic allergic reaction that affects multiple body systems simultaneously, involving skin symptoms, respiratory distress, cardiovascular symptoms, and gastrointestinal issues 1.

Key Differences

• Urticaria is typically limited to the skin, while anaphylaxis affects multiple body systems
• Anaphylaxis involves respiratory distress, cardiovascular symptoms, and gastrointestinal issues, which are not typically seen in urticaria
• Anaphylaxis is a medical emergency requiring immediate intervention, whereas urticaria can typically be managed in an outpatient setting

Diagnosis and Treatment

• The NIAID/FAAN diagnostic criteria for anaphylaxis include acute onset of illness with involvement of the skin, mucosal tissue, or both, with either respiratory involvement or reduced blood pressure and/or associated symptoms of end-organ dysfunction 1
• Treatment for urticaria usually involves antihistamines like cetirizine or diphenhydramine, while anaphylaxis requires immediate epinephrine administration (0.3-0.5mg intramuscularly for adults, 0.15mg for children under 30kg), followed by antihistamines, corticosteroids, and supportive care 1
• Epinephrine administration is the first-line treatment for anaphylaxis, and it should not be delayed or withheld, even if the diagnostic criteria are not fully met 1

Clinical Judgment

• Clinician judgment is crucial in diagnosing and managing anaphylaxis, as the condition can present with varying degrees of severity and the diagnostic criteria may not always be met 1
• Isolated allergen-associated urticaria should be distinguished from anaphylaxis, and prompt epinephrine administration is indicated for anaphylaxis, while antihistamines may be sufficient for urticaria 1

From the FDA Drug Label

The signs and symptoms associated with anaphylaxis include flushing, apprehension, syncope, tachycardia, thready or unobtainable pulse associated with hypotension, convulsions, vomiting, diarrhea and abdominal cramps, involuntary voiding, airway swelling, laryngospasm, bronchospasm, pruritus, urticaria or angioedema, swelling of the eyelids, lips, and tongue. Epinephrine also alleviates pruritus, urticaria, and angioedema and may relieve gastrointestinal and genitourinary symptoms associated with anaphylaxis because of its relaxer effects on the smooth muscle of the stomach, intestine, uterus and urinary bladder

The main difference between urticaria and anaphylaxis is that:

• Urticaria is a symptom characterized by hives or itchy skin, which can be a part of an allergic reaction, but it is not life-threatening on its own.
• Anaphylaxis is a severe, life-threatening allergic reaction that can cause a range of symptoms, including urticaria, as well as other more serious symptoms such as hypotension, bronchospasm, and airway swelling. Key symptoms of anaphylaxis include:
• Flushing
• Apprehension
• Syncope
• Tachycardia
• Hypotension
• Convulsions
• Vomiting
• Diarrhea
• Abdominal cramps
• Involuntary voiding
• Airway swelling
• Laryngospasm
• Bronchospasm 2 2

From the Research

Difference Between Urticaria and Anaphylaxis

• Urticaria is a common condition characterized by wheals and/or angioedema, whereas anaphylaxis is a life-threatening systemic reaction that involves multiple organ systems 3.
• The symptoms of urticaria and anaphylaxis can be similar, but anaphylaxis is typically more severe and can include symptoms such as difficulty breathing, mucosal swelling, and cardiovascular symptoms 4, 5.
• The causes and triggers of acute urticaria and anaphylaxis are similar, but some peculiarities can be observed, such as the role of mast cells in the physiopathology of both conditions 3.
• The diagnostic approach may differ between urticaria and anaphylaxis, depending on the condition, suspicious causes, age groups, and regions 3.
• The treatment of urticaria and anaphylaxis also differs, with adrenaline being the first-line treatment for anaphylaxis, and H1-antihistamines being the first choice for acute urticaria 3, 6.

Key Characteristics of Urticaria and Anaphylaxis

• Urticaria:
  • Common condition characterized by wheals and/or angioedema
  • Can be acute or chronic
  • Typically not life-threatening
  • Treatment: H1-antihistamines, antihistamines, and immunomodulators 3, 7, 6
• Anaphylaxis:
  • Life-threatening systemic reaction
  • Involves multiple organ systems
  • Symptoms can include difficulty breathing, mucosal swelling, and cardiovascular symptoms
  • Treatment: Adrenaline, supportive care, and adjunct medications such as histamine H1 and H2 antagonists, corticosteroids, beta2 agonists, and glucagon 4, 5, 6

Similarities and Differences in Clinical Management

• Both urticaria and anaphylaxis require a thorough clinical evaluation to determine the underlying cause and develop an appropriate treatment plan 7, 6.
• The management of urticaria and anaphylaxis may involve patient education, avoidance of triggers, and pharmacologic treatment 5, 3, 6.
• Anaphylaxis requires immediate recognition and treatment, whereas urticaria can often be managed on an outpatient basis 4, 6.