Patatin has recently been identified as the 42 kDa major food allergen of potato (Sol t 1). Although potato allergy is rare, we have identified five potato allergic patients with positive skin prick tests and positive DBPC food challenges. Symptoms ranged from atopic dermatitis to food anaphylaxis in these patients, many of whom have been hospitalized numerous times after eating potato. Serum from these patients selectively identified and verified patatin as a major allergen from potato tubers by immunoblotting patatin pro tein purified from plants or total protein from potato tuber extracts.All patients indentified the 42 kDa patatin protein. The genes for patatins, a large gene family composed of numerous isofonns and which represent 40% of potato tuber protein, have been isolated many years ago. The availability of DNA and protein sequences allowed us to utilize positive IgE binding from each patient to identify the IgE binding epitopes of patatin. By synthesizing 89 over lapping decamer oligopeptides representing the full patatin primary amino acid sequence, we have identified the major and minor IgE binding epitopes of this allergen. Subsequently, we have identified within these epitopes, substitutions in amino acid residues that appear to reduce or abolish IgE binding to these peptides. By identifying amino acid sequences that potentially reduce IgE binding, it may be possible to engineer patatins with reduced allergenicity for use in immunotherapy and other applications.