A microtechnique is described to visualize pollen allergens by making prints from the surface of mature grains on nitrocellulose membrane. The allergen Lol p I is detected by specific monoclonal antibodies or specific IgE from sera of grass-pollen-allergic patients, visualized by the immunoperoxidase method. This technique offers the potential to study the distribution of individual allergens in aerobiology samples by bright-field microscopy, and to determine the sensitivity spectra of allergic individuals to known and unknown pollen sources.