The concept of 'one airway, one disease' refers to the frequent comorbidity of asthma and rhinitis. However, only limited research has been done on this association for the diverse range of occupational respiratory sensitisers. The relative frequency of rhinitis was determined for the 15 respiratory sensitisers reported to cause at least 10 cases of rhinitis or asthma to The Health and Occupation Reporting (THOR) network between 1997 and 2006. Of 1408 cases, 1190 were sole diagnoses of asthma, 138 sole diagnoses of rhinitis and in 80 cases asthma coexisted with rhinitis. The six sensitisers for which rhinitis featured in over 15% of cases were all particulates and known to cause release of mast cell mediators, either directly or through IgE antibodies. Four of the other nine sensitisers often exist as vapours and only two have been consistently associated with IgE-mediated disease mechanisms. Particle size did not appear to correlate with the relative frequency of rhinitis. Despite its limitations this study would support the hypothesis that there are at least two mechanistic categories of respiratory sensitisation with rhinitis being relatively more common where the mechanism is IgE-mediated. Particulate nature may be another important factor to consider in future studies.