BACKGROUND Although many studies have examined chronic asthma, limited data exist on acute immunopathogenic events induced by allergens. The aim of the study was to investigate the acute cellular, serologic and histopathologic events in airway inflammation produced by intranasal challenge of mice sensitised to the major house dust mite allergen Der p 1. METHODS C57BL/6 mice were immunised subcutaneously with Der p 1 in alum. Mice were bled and challenged intranasally with Der p 1 on day 14 and killed on day 17. Lungs were fixed in situ, processed and stained with haematoxylin and eosin. The degree of inflammation and eosinophil infiltration was quantified by image analysis. Specific IgE was determined by passive cutaneous anaphylaxis. Cells from spleen and draining lymph nodes were cultured for 24 h with Der p 1, and IL-3/GM-CSF released into supernatants was measured by bioassay. RESULTS Intranasal challenge of sensitised mice induced eosinophilic influx into the large and small airways and the alveolar regions of the lung, mucus plugging and in severe cases numerous Charcot-Leyden crystals. The quantitation of the inflammation induced by different sensitisation and challenge doses showed that optimal inflammation could be produced using only 1 microg of allergen for both sensitisation and challenge. The degree of inflammation was not related to the titre of IgE antibody and was indeed produced in its absence. T cell reactivity of spleen cells to the allergen was decreased suggesting cell migration or inactivation. CONCLUSIONS Mice sensitised and challenged intranasally with as little as 1 microg of Der p 1 produced an extensive pulmonary eosinophilic inflammation which shared many of the features of the inflammation found in asthma. The small amount of allergens required and the use of intranasal challenge should provide a useful model.