Anaphylaxis is a serious generalized or systemic hypersensitivity reaction that is rapid in onset and potentially fatal.

Diagnosis can be made if it is acute in onset of minute to several hour duration that involves the skin, mucosal tissue or both plus having signs & symptoms either respiratory or cardiovascular compromise.

It involves immunological response with IgE, IgG or immune complexes. Non-immunological mechanisms are also involved and termed as nonallergic anaphylaxis that is relatively uncommon in children.

Protracted, severe anaphylaxis are reactions occurring up to 32 hours despite aggressive management.



Patient Observation

  • Considered in post-anaphylactic patients due to possible recurrence as the effect of epinephrine wears off and risk of biphasic reaction
  • Children <16 years should be admitted for observation; young people ≥16 years should be observed for 6-12 hours from onset of symptoms
  • Biphasic reaction occurs in 1-23% of anaphylaxis cases
    • Onset of the 2nd phase of reaction ranges from 1-72 hour after the initial reaction
  • The period of observation will vary from 4-24 hours depending on the clinical situation
    • Patients with respiratory symptoms would require 6-8 hours observation
    • Patients with hypotension/shock require 12-24 hours observation in ICU
  • Patients should be followed-up for 7 days after the observational period for occurrence of biphasic reactions


Allergy and Anaphylaxis Prevention

  • In the history, take note of allergy record of patient’s parents, siblings, relatives on maternal- or paternal-side
    • Predictive family score may be used to identify patients at-risk of developing allergy
    • A family history of asthma and allergy identifies children at high risk for developing allergic disease

Avoidance Management

  • Should be individualized based on factors such as age, occupation, activity, hobbies, environment, patient’s level of anxiety and access to medical care
  • Avoidance of co-triggers (food, NSAIDs, alcohol) and exercise during extreme weather can help prevent exercise-induced anaphylaxis and food-dependent exercise-induced anaphylaxis
  • Delaying of food ingestion 2-4 hours prior to exercise may prevent food-dependent exercise-induced anaphylaxis
  • Patient education is the most important strategy since avoidance measures may not always be successful
    • Educating patients or caregivers on self-management of anaphylaxis is important
    • Should include emphasis on hidden allergens, risk of future anaphylaxis, cross-reactivity between drugs and various allergens
  • Know the possible risk factors contributing to severe anaphylaxis resulting from injections of immunotherapy with measures for prevention and management of severe systemic allergic reactions

Other Approaches

  • Pharmacologic prophylaxis (eg antihistamines, glucocorticosteroids)
    • May help prevent idiopathic anaphylaxis, recurrent anaphylaxis to radiographic materials
  • Venom immunotherapy (VIT)
    • Recommended as therapy for venom allergy in children and adults
    • Found to be effective in up to 98% of patients with history of venom-induced anaphylaxis
    • Studies show that a 3-5 year course of SC immunotherapy with insect venom can prevent recurrences of insect venom anaphylaxis
  • Drug desensitization
    • An alternative therapy for drug-induced anaphylaxis of patients unresponsive/intolerant to traditional therapies
    • Done by continuously administering the drug allergen at increasing doses over a short period of time, until the therapeutic dose is reached

Breastfeeding and Milk Formulas

  • Exclusive breastfeeding of infants until 4-6 months is recommended, especially in children at high risk of allergic disease
    • Reported protection against allergic disease in the early years of life is relatively small, and some studies suggest an increased risk of disease in later life
  • Evidence to support dietary changes for breastfeeding mothers to prevent food allergy in their child is also lacking
  • If breastfeeding is not possible in high risk infants, a hydrolyzed formula is recommended
  • Extensively hydrolyzed casein and partially hydrolyzed whey formulas have been shown to have preventive effects
    • These effects have only been demonstrated in high risk infants with atopic heredity
  • Prospective studies have shown that soy formula and other milks (eg goat’s formula) are not recommended for the reduction of food allergy risk
  • More studies are needed to support the use of probiotics/prebiotics for infant diet supplementation

Solid Food

  • It is recommended that introduction of solid food, including those with potential allergens, should be done at the age of 4-6 months, without delay
    • There is insufficient evidence that dietary restriction should be done for high risk patients, thus not recommended
  • Introduction of peanuts into the diet of ≥6-month old infants with mild-moderate atopic dermatitis is recommended
    • For infants aged 4-6 months with severe atopic dermatitis, egg allergy, or both, consider IgE measurement prior to introduction of peanut-containing foods

Referral To An Allergist-Immunologist

  • Patients should be referred to age-specific allergy specialist at the earliest possible time after the reaction
  • Referral to an allergist-immunologist is indicated in the following circumstances:
    • To take a full allergy-focused history
    • To perform tests to determine the cause of anaphylaxis and confirm the diagnosis
    • To develop an individualized management plan and be able to train the patient and caregivers to ensure implementation of management plan
    • To offer information on avoidance and control of confirmed trigger factors
    • If symptoms are recurrent or difficult to control
    • If patient is a candidate for immunotherapy or desensitization
    • If daily medications for prevention is required
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