What are the signs of anaphylaxis?

Signs of Anaphylaxis

Anaphylaxis presents with a constellation of acute symptoms involving multiple organ systems, and while barking cough is not a classic sign, respiratory symptoms including cough, stridor, and throat tightness are key features of upper airway involvement in anaphylaxis. 1

Key Clinical Manifestations by Organ System

Respiratory Tract Signs (Most Critical)

• Stridor (upper airway obstruction) 1
• Cough (can be present as part of respiratory involvement) 1
• Hoarseness and dysphonia 1
• Throat tightness and throat itching 1
• Wheezing and bronchospasm (lower airway) 1
• Shortness of breath and difficulty breathing 1
• Chest tightness 1
• Cyanosis 1

Cutaneous Signs (Most Common but May Be Absent)

• Urticaria (hives) and angioedema are the most common manifestations, but may be delayed or completely absent in rapidly progressive anaphylaxis 1, 2
• Diffuse erythema (flushing) 1, 2
• Pruritus (itching) 1, 2
• Swelling of eyelids, lips, and tongue 2

Cardiovascular Signs (Life-Threatening)

• Tachycardia (the rule in anaphylaxis) 1
• Hypotension 1, 2
• Weak or thready pulse 1, 2
• Syncope and collapse 1, 2
• Dizziness 1, 2
• Cardiac arrhythmias 1
• Incontinence 1, 2

Gastrointestinal Signs

• Nausea and vomiting 1, 2
• Crampy abdominal pain 1, 2
• Diarrhea 1, 2

Neurological Signs

• Altered mental status and confusion 1
• Sense of impending doom 1
• Behavioral changes (particularly in infants) 1
• Headache 1
• Tunnel vision 1
• Convulsions 2
• Loss of consciousness 1

Critical Timing and Progression

Anaphylaxis typically develops within minutes of exposure to the trigger, and the more rapidly symptoms appear, the more severe and life-threatening the reaction is likely to be. 1, 3

• Symptoms usually begin within minutes but can develop up to several hours after exposure 1
• Hemodynamic collapse can occur rapidly (within 10 minutes) with little or no cutaneous or respiratory manifestations due to massive fluid shift from intravascular to extravascular space 1, 3
• Biphasic reactions can occur 8-12 hours after the initial episode 1
• Protracted anaphylaxis may last up to 32 hours despite treatment 1

Important Clinical Pitfalls

Regarding "Barking Cough"

While barking cough is classically associated with croup (laryngotracheobronchitis), cough is listed as a respiratory manifestation of anaphylaxis 1. The presence of stridor (which can sound similar to barking cough) is specifically mentioned as a sign of upper airway involvement in anaphylaxis 1. If a patient presents with barking cough along with other signs of anaphylaxis (skin changes, cardiovascular symptoms, gastrointestinal symptoms), anaphylaxis must be considered and treated immediately with intramuscular epinephrine. 1, 4

Skin Signs May Be Absent

Up to 20% of patients with anaphylaxis may have no cutaneous manifestations, particularly in rapidly progressive cases with cardiovascular collapse 1, 5. Do not wait for hives or flushing to appear before treating suspected anaphylaxis 1, 3.

Differential Diagnosis Confusion

Vasovagal reactions are most commonly confused with anaphylaxis, but vasovagal episodes have bradycardia (not tachycardia), no urticaria, no bronchospasm, and cool/pale skin rather than flushed skin 1. Other conditions to consider include acute asthma, foreign body aspiration, and anxiety attacks 1.