Anaphylaxis

• Urticaria: Itching, raised red welts on the skin.
• Angioedema: Swelling, often around the eyes and lips, sometimes throat.
• Atopic Dermatitis: Chronic, relapsing eczema; often a history of other atopic conditions.

• Food Allergies: Rapid onset after ingestion; symptoms include hives, swelling, respiratory distress.
• Insect Stings: Sudden symptoms after sting; includes hives, bronchospasm, hypotension.
• Drug-Induced: Commonly seen with antibiotics, NSAIDs; presents with multisystem involvement.

• Vasovagal Syncope: Triggered by stress or pain; presents with bradycardia, pallor, sweating.
• Panic Attacks: Presents with hyperventilation, chest pain, palpitations; no triggers like allergens.
• Septic Shock: Fever, hypotension, tachycardia; evidence of infection.

• Acute Myocardial Infarction: Central chest pain, diaphoresis, radiation to jaw/arm.
• Cardiogenic Shock: Severe hypotension, jugular venous distension, peripheral edema.
• Pulmonary Embolism: Sudden onset dyspnoea, pleuritic chest pain, haemoptysis.

• Asthma Exacerbation: Wheezing, dyspnoea, response to bronchodilators.
• Choking/Foreign Body: Sudden onset, witnessed aspiration, stridor.
• Vocal Cord Dysfunction: Stridor, sensation of throat tightness, often without hypoxia.

Sudden onset of symptoms suggests anaphylaxis, especially if symptoms develop within minutes to an hour after exposure to a known allergen. Gradual onset may suggest other causes such as panic attacks or systemic infections.

Ask about recent exposure to potential allergens such as foods, insect stings, medications, or latex. A known allergy with recent exposure is highly suggestive of anaphylaxis.

Enquire about symptoms like wheezing, shortness of breath, or stridor, which suggest airway involvement in anaphylaxis. Differentiating from other causes like asthma or foreign body aspiration is crucial.

Look for signs such as dizziness, hypotension, or syncope, which may suggest anaphylaxis, especially in the context of allergic exposure. Differential considerations include vasovagal syncope and cardiogenic shock.

Urticaria, flushing, and angioedema are common in anaphylaxis. Absence of skin involvement should not rule out anaphylaxis, but may warrant considering alternative diagnoses such as septic shock or panic attacks.

Include past medical history of atopic conditions (asthma, eczema, allergic rhinitis), previous anaphylactic episodes, and known allergies. Drug history is important, particularly antibiotics, NSAIDs, and new medications. Family history of anaphylaxis may increase suspicion. Social history should include occupation (e.g., healthcare workers are at risk for latex allergy).

Serum tryptase levels can be elevated in anaphylaxis, but the test may not always be available or useful in acute settings. Consider full blood count, renal function, liver function tests, and lactate to assess overall status and rule out other conditions.

Chest X-ray may be warranted if there is concern for foreign body aspiration, pneumothorax, or other respiratory complications. However, imaging is not typically required in the acute management of anaphylaxis.

In stable patients, referral for skin prick testing or specific IgE blood tests to identify triggers is recommended. This is not part of acute management but is crucial for long-term management and prevention.