Can allergies cause vomiting?

Can Allergies Cause Vomiting?

Yes, allergies can definitely cause vomiting—it is a well-recognized gastrointestinal manifestation of both IgE-mediated and non-IgE-mediated food allergies, occurring either as an isolated symptom or as part of a systemic allergic reaction including anaphylaxis. 1

Mechanisms and Clinical Presentations

Vomiting occurs through multiple allergic pathways:

IgE-Mediated Food Allergy

• Vomiting typically develops within minutes to 2 hours after food ingestion as part of an immediate hypersensitivity reaction 1, 2
• The mechanism involves mast cell degranulation in the gastrointestinal tract, releasing histamine and other mediators that act on mucous glands and trigger the vomiting reflex 1
• Vomiting was reported in 22% of patients with oral food challenge-proven alpha-gal allergy, demonstrating it as a common allergic symptom 1
• In anaphylaxis specifically, vomiting is listed among the cardinal signs and symptoms alongside flushing, syncope, tachycardia, hypotension, convulsions, diarrhea, and abdominal cramps 3

Non-IgE-Mediated Food Allergy

• Food protein-induced enterocolitis syndrome (FPIES) characteristically presents with severe vomiting starting 2 hours after ingestion, often accompanied by lethargy and sometimes hypotension and acidosis 1
• Infants with non-IgE food allergies commonly present with vomiting, diarrhea (particularly with blood), poor growth, and malabsorption 1
• These delayed reactions occur within several hours to days after ingestion and are typically skin prick test negative 2

Common Food Allergens Causing Vomiting

The eight most common food allergens responsible for over 90% of IgE-mediated reactions are: cow's milk, hen's egg, soy, peanuts, tree nuts (and seeds), wheat, fish, and shellfish 2

• Cow's milk is the most common offender among foodstuffs causing gastrointestinal symptoms including vomiting 4
• Alpha-gal syndrome (allergy to mammalian meat) causes delayed vomiting 1-7 hours after eating beef, pork, or other mammalian products 1

Critical Diagnostic Considerations

When to Suspect Food Allergy

• Vomiting occurring within minutes to hours after specific food ingestion, especially if reproducible on multiple exposures 1
• Infants with recalcitrant gastroesophageal reflux where symptoms don't respond to standard therapies (about 40% may have food allergy) 1
• Vomiting accompanied by other allergic symptoms such as urticaria, angioedema, itching, wheezing, or respiratory symptoms 1, 5

Important Pitfalls to Avoid

• A positive skin prick test or serum IgE test alone does NOT diagnose food allergy—these tests detect sensitization but require clinical correlation with symptoms 1
• In one study, 93% of children avoiding foods based solely on positive tests were actually tolerant when challenged 1
• Vomiting can be misattributed to food intolerance rather than true allergy, but distinguishing between them is critical since food intolerance is not immune-mediated and doesn't carry anaphylaxis risk 1

Management Algorithm

Immediate Assessment

1. Evaluate for anaphylaxis: Check for respiratory compromise (wheezing, shortness of breath), cardiovascular symptoms (hypotension, tachycardia), or widespread skin involvement 1, 6
2. If anaphylaxis is present, administer intramuscular epinephrine immediately—this is the only first-line treatment with no substitute 1, 7, 3

Adjunctive Treatment for Vomiting

• H1 antihistamines (diphenhydramine 1-2 mg/kg, maximum 50 mg) help relieve symptoms but should never replace epinephrine in anaphylaxis 1, 7
• H2 antihistamines (ranitidine 1-2 mg/kg, maximum 75-150 mg) may be added, as the combination works better than either alone 7
• Corticosteroids (prednisone 1 mg/kg, maximum 60-80 mg) may prevent biphasic reactions, though evidence is limited 1, 7

Diagnostic Workup

• Obtain detailed history focusing on temporal relationship between food ingestion and symptom onset 1
• Perform skin prick testing or serum food-specific IgE testing to identify likely allergens 1
• For delayed reactions or negative testing, elimination diets followed by oral food challenges may be necessary to definitively identify the culprit food 1

Long-Term Management

• Strict avoidance of identified food allergens is the mainstay of management 1, 2
• Prescribe epinephrine auto-injector (2 doses) for patients with IgE-mediated food allergy, especially those with prior anaphylaxis 1, 7
• Provide comprehensive education on label reading, cross-contamination risks, and recognition of anaphylaxis symptoms 1
• Schedule follow-up within 6-12 months to reassess tolerance, as many children outgrow allergies to milk, egg, soy, and wheat by school age 2

Special Populations

Infants and young children have the highest incidence of gastrointestinal food allergies, with symptoms often beginning in the first 2 years of life 8, 2

Alpha-gal syndrome patients may present with isolated GI symptoms (including vomiting) without skin or respiratory findings, making diagnosis challenging without specific IgE testing 1