Fennel allergy is a lipid-transfer protein (LTP)-related food hypersensitivity associated with peach allergy.

Fennel allergy has been rarely reported, and the association with peach allergy has never been described. Our aim was to (i) study the correlation between symptom severity of peach and fennel and (ii) identify fennel allergens and the role of rPru p 3 antibodies in severe reactions to fennel. In 148 patients with peach allergy, we investigated 58 patients with symptoms and IgE antibodies positive to fennel. IgE to rPru p 1, 3, and 4 and rBet v 1, 2, and 4 were measured by immunoblotting, and the N-terminal amino acid sequences and relevant allergens were determined. We found significant association between severe reactions to fennel and peach (p = 0.0009). A major allergen was ~9 kDa lipid-transfer protein (LTP), cross-reactive with Pru p 3, a 15 kDa protein identified as a pathogenesis-related protein 1 of the Bet v 1 family. In conclusion, peach and fennel severe allergic symptoms are significantly related, and LTP is a major fennel allergen. Fennel should be included in the LTP syndrome.