Red vs. Green Pepper Allergy: Can You React to One and Not the Other?

Yes, it's possible to react to red bell peppers but tolerate green (or vice versa). They are the same species (Capsicum annuum) at different ripeness stages, but allergen profiles change during ripening.

Why Reactions Differ

• Protein composition changes: Ripening alters expression of allergenic proteins (e.g., profilin, lipid transfer proteins, thaumatin-like proteins).
• Concentration differences: Some allergens increase (capsaicinoids in hot peppers; bell peppers have minimal capsaicin).
• Cross-reactivity patterns: Sensitization to pollen (birch, mugwort) or latex drives reactions to specific pepper proteins via cross-reactivity (oral allergy syndrome).

Nightshade Family Context

Peppers, tomatoes, potatoes, eggplants share some allergens (e.g., profilin, patatin-like proteins). Sensitivity varies by individual and specific protein.

Clinical Approach

1. Detailed history: Which peppers, preparation (raw/cooked), associated symptoms (oral itching vs. systemic).
2. Testing: Skin prick with fresh red/green pepper extracts; component-resolved diagnostics (CRD) for specific proteins.
3. Oral food challenge: Gold standard, under supervision.

Management

• Avoid reactive varieties/preparations.
• Cooking may denature heat-labile allergens (profilin) but not stable ones (LTPs).
• Epinephrine auto-injector if systemic reactions occurred.
• Consult allergist for personalized plan.

Component testing clarifies which proteins drive reactivity, predicting cross-reactivity with other foods.