For the peptide array, peptides of 20 aminoacids are synthesized of a specific allergen, with an offset of 2 aminoacids. These peptides are printed on a glass slide. The slides are incubated with serum from an allergic patient. Binding of IgE or IgG4 to the peptide is detected with 2 fluorescent antibodies. Then, the slides are scanned and the fluorescence is digitized. The extent of fluorescence is a measure for the extent of IgE or IgG4 binding. This technique provides insight into the immunodominant epitopes of an allergen with respect to IgE/IgG4 binding. Furhtermore, the pattern of recognition or the number of epitopes recognized can be correlated with the severity of the allergic reaction.