Anaphylaxis history and symptoms

The hallmark of anaphylaxis is to find a possible causative allergen. Often the history may rely on friends and family who can help with the temporal relationship between symptoms and the inciting event. ^[1]

The diagnosis is likely when any one of the following criteria is met: ^[2]

• 1. Acute onset with involvement of mucosal tissue, skin, or both and one of the following:
  • Respiratory compromise
  • Reduced blood pressure or evidence of end-organ dysfunction
• 2. Exposure to a likely antigen for the patient followed by two of the following:
  • Skin involvement
  • Respiratory compromise
  • Reduced blood pressure
  • Gastrointestinal symptoms
• 3. Exposure to a known allergen to the patient followed by reduced blood pressure

Symptoms of anaphylaxis are related to the histamine release from mast cells (degranulation). Histamine induces vasodilation of arterioles and constriction of bronchioles in the lungs. ^[3]

Patients with anaphylaxis may have a positive history of: ^{[4] [5]}

• Ingestion of certain foods, drinks or medications within 8 hours before the event
• Exposure to heat or cold before the event
• Sting or bite prior to the event
• Recurrence of symptoms following initial resolution
• Recent infection or illness
• Recent relevant exposure or travel history
• Prior similar episodes

Common symptoms of anaphylaxis include:

• Urticaria (hives)
• Respiratory distress
• Upper Airway edema
• Itching
• Nasal congestion
• Flushed appearance
• Hypotension (low blood pressure)
• Stridor
• Rhinitis
• Dizziness
• Confusion
• Headache
• Abdominal pain
• Cough
• Diarrhea
• Palpitations
• Vomiting

Less common symptoms of anaphylaxis include:

• Chest pain
• Polyuria
• Slurred speech
• Tears (due to angioedema and stress)
• Unconsciousness
• Encephalitis
• Fainting
• Angioedema (swelling of the lips, face, neck and throat)
• Anxiety

The time between ingestion of the allergen and anaphylaxis symptoms can vary for some patients depending on the amount of allergen consumed and their reaction time. Symptoms can appear immediately or can be delayed by half an hour to several hours after ingestion. However, symptoms of anaphylaxis usually appear very quickly once they do begin.

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