Anaphylaxis

1. If any one of the following three criteria is met, the likelihood of anaphylaxis is very high:

Acute onset (within minutes to several hours) of skin and/or mucosal symptoms (e.g., generalized urticaria, pruritus, flushing, or swelling of lips, tongue, or uvula) plus at least one of the following:

 a. Respiratory compromise (e.g., dyspnea, wheezing/bronchospasm, stridor, reduced peak expiratory flow, hypoxemia)

 b. Reduced blood pressure or symptoms of end-organ dysfunction (e.g., hypotonia [collapse], syncope, incontinence

2. Two or more of the following symptoms that occur rapidly after exposure to a likely allergen (within minutes to two hours):

 a. Involvement of skin or mucosal tissue (e.g., generalized hives, pruritus or flushing, swollen lips–tongue–uvula)

 b. Respiratory compromise

 c. Reduced blood pressure or associated symptoms

 d. Persistent gastrointestinal symptoms (e.g., abdominal pain, vomiting)

3. Reduced blood pressure after exposure to a known allergen (within minutes to several hours):

  In children: systolic blood pressure lower than age-appropriate norms or a decrease of >30% from baseline

  In adults: systolic blood pressure <90 mmHg or >30% decrease from baseline

Blood tests are not essential for the diagnosis of anaphylaxis, but measuring mediators involved in the anaphylactic mechanism, such as tryptase and histamine, can be helpful in differential diagnosis.

-Securing the airway to ensure effective breathing and evaluating circulatory status should be done promptly, followed by laying the patient down with their legs elevated and initiating medication administration without delay. 

- Intramuscular injection of epinephrine (1:1000, 1 mg/mL) should be given as soon as possible into the outer thigh

   0.01 mg/kg in children (maximum single dose: 0.3 mg) and 0.3–0.5 mg in adults (maximum single dose: 0.5 mg)

- If severe hypotension or other symptoms persist after the intramuscular injection, repeat intramuscular injections may be given at 10–15 minute intervals. 

- In cases where the patient is already in shock, continuous intravenous infusion of epinephrine (1:10000) may be considered.

- Antihistamines, bronchodilators, and corticosteroids are considered secondary treatments (Not be used alone in the initial treatment of anaphylaxis without the administration of epinephrine)

- The use of corticosteroids is more for the prevention of biphasic reactions rather than for treating acute symptoms and signs. 

- To monitor for possible biphasic reactions, patients who experienced respiratory distress should be observed for 6–8 hours, and those with hypotension should be monitored for 12–24 hours. 

- For patients at risk of recurrence, a prescription for an epinephrine auto-injector is necessary, along with education on allergen avoidance and proper use of the auto-injector.