Background: Only 2 allergenic proteins have been described in lettuce allergy: a 16-kDa protein (putative profilin) and a lipid transfer protein (LTP) named Lac s 1.

Objective: Our aim was to identify the allergens involved in the anaphylactic reactions of 2 patients who had eaten lettuce.

Methods: The study was performed by Ig (immunoglobulin)–E immunodetection and immunodetection-inhibition assays.

Results: Both patients’ sera showed specific IgE binding to a single protein from the crude lettuce extract (apparent molecular weight of 14 kDa). To characterize the allergen detected, the lettuce extract underwent proteolytic digestion and heat treatment and was highly resistant to both. The patients’ sera also recognized the major peach allergen Pru p 3 by immunodetection. When the lettuce allergen was incubated with both Pru p 3 from peach peel and recombinant Pru p 3, the immunodetection-inhibition assay indicated that patients were sensitized to the lettuce LTP Lac s 1.

Conclusions: The allergen involved in the lettuce-induced anaphylaxis of our patients was the LTP Lac s 1.

Key words: Allergy. Anaphylaxis. Lettuce allergy. Lipid transfer protein.