What are the possible causes of nausea when eating eggs in a patient in their 70s?

Possible Causes of New-Onset Nausea from Eggs in a 70-Year-Old Patient

The most likely causes are new-onset egg allergy (though uncommon at this age), age-related changes in gastric motility or acid production affecting egg digestion, or medication-related alterations in gastrointestinal function. 1

Primary Differential Diagnosis

Food Allergy (IgE-Mediated)

• Egg allergy can develop at any age, though it is more common in children, with eggs being one of the most frequent causes of anaphylactic episodes in pediatric populations 1
• In adults, new-onset food allergies are less common but can occur, with symptoms typically appearing within minutes to hours after ingestion 1
• Key distinguishing features: Look for associated symptoms beyond isolated nausea—pruritus, urticaria, angioedema, respiratory symptoms (wheezing, throat tightness), or gastrointestinal cramping 1
• If only nausea occurs without cutaneous, respiratory, or cardiovascular symptoms, IgE-mediated allergy is less likely 1

Food Protein-Induced Enterocolitis Syndrome (FPIES)

• While FPIES is predominantly a pediatric condition, it can present with isolated gastrointestinal symptoms including nausea and vomiting 1
• Symptoms typically occur 1-4 hours after ingestion (delayed compared to IgE-mediated reactions) 1
• This is a non-IgE mediated reaction, so standard allergy testing may be negative 1

Age-Related Gastrointestinal Changes

• Gastroparesis or delayed gastric emptying increases with age and can cause nausea, particularly with protein-rich foods like eggs 1
• Eggs are relatively high in fat (especially if prepared with butter or oil), which can exacerbate symptoms in patients with gastric dysmotility 1
• Reduced gastric acid production (achlorhydria) common in elderly patients may impair protein digestion 1

Medication-Induced Changes

• Many medications commonly prescribed to elderly patients can cause nausea or alter gastrointestinal function 2, 3
• Recent medication changes should be thoroughly reviewed, as drug-induced nausea is extremely common 2, 4
• Some medications may specifically affect protein or fat digestion 3

Gallbladder Disease

• Eggs are a classic trigger for cholecystitis or biliary colic due to their fat content stimulating gallbladder contraction 2, 3
• Consider this especially if nausea is accompanied by right upper quadrant pain occurring 30-90 minutes after eating eggs 3

Diagnostic Approach

Critical History Elements

• Timing of symptom onset: Immediate (minutes) suggests IgE-mediated allergy; 1-4 hours suggests FPIES or gastroparesis; 30-90 minutes suggests biliary disease 1, 3
• Associated symptoms: Skin changes, respiratory symptoms, or cardiovascular changes point toward allergy 1
• Medication review: Recent additions or dose changes of any medications 2, 3
• Preparation method: Fried or butter-cooked eggs may trigger symptoms related to fat content rather than egg protein itself 1, 3
• Tolerance of baked eggs: Patients with egg allergy may tolerate eggs in baked products (bread, cake), suggesting the issue is with egg protein structure 1

Recommended Testing

• Skin prick testing to egg proteins (both egg white and yolk) if IgE-mediated allergy is suspected 1
• Serum-specific IgE to egg proteins can be helpful when skin testing is not feasible 1
• Gastric emptying scintigraphy if gastroparesis is suspected based on symptoms of early satiety, postprandial fullness, or bloating 1
• Right upper quadrant ultrasound if biliary disease is suspected 3

Important Caveats

• Standardized egg extracts for skin testing are not currently available, so testing may need to be performed with fresh egg extracts by an experienced allergist 1
• Negative allergy testing does not exclude non-IgE mediated reactions like FPIES 1
• In elderly patients, symptoms are often poor predictors of functional versus pathological illness, requiring a lower threshold for investigation 4

Management Approach

Immediate Management

• Complete avoidance of eggs in all forms until diagnosis is established 1
• If severe allergic reaction is suspected (respiratory symptoms, hypotension, severe vomiting), the patient should carry epinephrine and be referred urgently to an allergist 1

Symptomatic Treatment

• Dopamine receptor antagonists (prochlorperazine 5-10 mg three to four times daily or metoclopramide) are first-line for nonspecific nausea 5, 6
• 5-HT3 receptor antagonists (ondansetron 4-8 mg two to three times daily) for persistent nausea 5
• H2 receptor antagonists (famotidine) only if gastritis or GERD is contributing 6

Definitive Diagnosis

• Supervised oral food challenge may be necessary if history and testing are inconclusive, but this should only be performed by experienced personnel with resuscitation equipment immediately available 1
• In patients with suspected severe reactions, challenges should be performed in a hospital setting 1

Key Clinical Pitfalls to Avoid

• Do not assume this is simply "food intolerance" without proper evaluation—true allergic reactions can be life-threatening 1
• Do not use proton pump inhibitors as first-line treatment unless there is specific evidence of gastritis or GERD 5, 6
• Do not perform food challenges without appropriate emergency equipment and trained personnel 1
• Do not forget to review all medications—drug-induced nausea is one of the most common and easily reversible causes 2, 3