Overview of Lentil Allergy and Its Major Allergens

Lentils (Lens culinaris) are a widely consumed legume, particularly prominent in Mediterranean, Middle Eastern, Asian, and North American diets. However, lentils are a notable source of food allergens that can provoke IgE-mediated hypersensitivity reactions, ranging from mild oral allergy syndrome to severe anaphylaxis.

Two primary protein allergens identified in lentils are:

• Len c 1 – A 7/8S globulin (gamma-vicilin seed storage protein)
• Len c 3 – A non-specific lipid transfer protein (nsLTP)

Biochemical Properties of Len c 1 and Len c 3

Len c 1 is considered the major allergen in lentils. It belongs to the vicilin family of seed storage proteins, which are commonly implicated in legume-induced allergic reactions.

Len c 3, while present in lower concentrations, is a potent nsLTP. These proteins are known for their structural stability and their role in severe, systemic allergic reactions, particularly in LTP-sensitised individuals.

Exposure and Geographic Prevalence

Lentil allergy primarily manifests via the oral ingestion route, although inhalational exposure (e.g., during cooking) has also been reported.

This condition is most frequently diagnosed in regions with high lentil consumption, including:

• Southern Europe (especially Spain and Italy)
• The Middle East
• South Asia
• North America

Cross-Reactivity with Other Legumes

Recent literature underscores the high degree of cross-reactivity between lentil allergens and other legume proteins:

• Len c 1 shares homologous IgE-binding epitopes with:
  • Ara h 1 (peanut)
  • Pis s 1 (pea)
  • Cic a 1 (chickpea)

These vicilin-type allergens contribute to overlapping allergic responses, explaining clinical cross-reactivity between lentils, chickpeas, peas, and peanuts.

Len c 3 also exhibits cross-reactivity with Pru p 3 from peach, an nsLTP involved in LTP syndrome common across southern Europe.

Thermal Stability and Allergenicity

Lentil allergens demonstrate variable heat stability:

• Some IgE-binding proteins are heat-labile, reducing allergenicity upon cooking.
• However, Len c 1 and Len c 3 are heat-stable and retain allergenic potential even after thermal processing.

Boiled lentil extracts have been shown to retain immunoreactive proteins, maintaining their ability to provoke allergic responses.

Diagnostic Value of Component-Resolved Testing (CRD)

Conventional extract-based testing often lacks specificity. The use of recombinant Len c 1 and Len c 3 in component-resolved diagnostics provides:

• Higher sensitivity
• Improved risk stratification
• Enhanced differentiation between true allergy and cross-reactive sensitisation

This molecular approach is especially beneficial in complex legume allergy cases involving multiple species.

Conclusion

Len c 1 and Len c 3 are pivotal in understanding lentil-induced allergic reactions. Their identification and inclusion in molecular allergy panels significantly improve diagnostic precision and guide personalised management strategies. With their structural resilience and cross-reactive potential, these proteins represent a clinically important frontier in legume allergy research.

References:

1. Vieths S, et al. Component-resolved diagnostics for legume allergy. Allergy. 2023.
2. Garcia-Blanco A, et al. Thermal stability of legume vicilin allergens. Clin Exp Allergy. 2024.
3. Sénéchal H, et al. Cross-reactivity among edible legumes: molecular insights. Mol Immunol. 2023.