Anaphylaxis and Food Allergy: Diagnosis and Treatment  

Diagnosis

Anaphylaxis is a clinical diagnosis. Findings may include:

• Flushing.
• Urticaria.
• Angioedema.
• Wheezing/stridor.
• Pre–syncope/hypotension.
• Nausea/vomiting.
• Diaphoresis.
• Rhinitis.
• Change of mental status.
• Incontinence.
• Hypovolemic shock.

History of exposure to common triggers should be elicited. A serum antibody test such as enzyme–linked immunosorbent assay (ELISA) or radioallergosorbent test (RAST) drawn concomitantly can help determine the inciting agent, if unknown. Skin testing must be delayed for 6 weeks from the time of exposure.¹

When diagnosis is uncertain, testing for levels of plasma histamine, 24–hour urine N–methyl–histamine, and serum/urine tryptase may be helpful.

Treatment

Cardiopulmonary monitoring and assessment (with intubation if required) and 2 high–volume intravenous access sites are immediately needed. The inciting agent should be removed, if possible. A tourniquet above the site of a venom sting or site of an allergy shot injection may be helpful.

Epinephrine (1:1000) should be administered intramuscularly for mild–to–moderate symptoms, or as soon as the diagnosis of anaphylaxis is considered. It may be self–administered with an EpiPen or similar device and can be repeated at 15–minute intervals en route to an emergency department.

Epinephrine (1:10,000) is used intravenously or through an endotracheal tube for severe symptoms. Glucagon is used intravenously in patients on beta–blockers who do not respond to epinephrine.²

Antihistaminic H1 and H2 blockers should both be used until anaphylaxis resolution. Diphenhydramine and cimetidine are given intravenously.
Oral agents should be considered when more intensive medical care is not immediately accessible.

Solumedrol is administered intravenously.

Inhaled beta–agonists may be used if bronchospasm is present.

If the patient is hypotensive, colloid or crystalloid intravenous fluid should be administered in large volumes. Pressors (dopamine, norepinephrine, phenylephrine, vasopressin) should be used for refractory hypotension.³

Patients with more than mild symptoms should be observed in the emergency department or admitted to the hospital for continued observation, due to risk of recrudescent symptoms after initial improvement.