Contact Dermatitis 2009: 61: 1–8  2009 John Wiley & Sons A/S Printed in Singapore. All rights reserved CONTACT DERMATITIS Patients with airborne sensitization/contact dermatitis from budesonide-containing aerosols ‘by proxy’ Marie Baeck 1 AND An Goossens 2 1 Department of Dermatology, Cliniques Universitaires Saint-Luc, Universit´ e Catholique de Louvain, Brussels, and 2 Department of Dermatology, University Hospital, K.U. Leuven, Belgium Background: Inhalation corticosteroids (CSs), despite their wide use, rarely cause sensitization in subjects administering them. Objective: To determine the cause of sensitization and/or of allergic contact dermatitis which occurred in air-exposed body areas of patients reacting to corticosteroids and to budesonide, in particular. Methods: We reviewed the patch test results and sensitization sources in patients who reacted positively to corticosteroids tested in the K.U. Leuven Dermatology department during an 18-year period. Results: Fifteen subjects, not themselves treated by budesonide-containing aerosols, but taking care of/or living together with patients who used them because of a chronic respiratory affection, appeared to have been sensitized by airborne exposure and/or presented with airborne allergic contact dermatitis from them. Conclusion: Air exposure to inhalation corticosteroids used ‘by proxy’ and to budesonide, in particular, needs to be taken into account as a potential cause of primary sensitization and/or airborne allergic contact dermatitis, sometimes also in an occupational context. Key words: airborne; allergic contact dermatitis; budesonide; ‘by proxy’; connubial; consort; corticosteroid; inhaled corticosteroids; primary sensitization.  John Wiley & Sons A/S, 2009. Conflicts of interest: The authors have declared no conflicts. Accepted for publication 18 March 2009 Despite the wide use of inhaled corticosteroids (CSs), few cases of asthmatic patients experiencing allergic reactions have been reported (1–18). Isaks- son et al. (3), who examined patients suffering from asthma or allergic rhinitis treated with tixocortol pivalate, observed a corticosteroids sensitization rate of 1.4%; among non-asthmatic patients, however, the rate of sensitization was 0.9%, the difference being not statistically significant. Raison-Peyron et al. (19) were the first authors to describe connubial or consort contact dermatitis from an inhalation corticosteroid-containing budes- onide in the mother of a 3-year old boy treated for asthma. Moreover, Ponten (20) and also more recently Corraza (21) reported on airborne contact dermatitis from occupational exposure to such aerosols, notwithstanding the extremely low concen- trations involved (20). Materials and methods We reviewed the patch test results and sensitization sources in patients who reacted positively to corti- costeroids obtained during an 18-year study period, i.e. from January 1, 1990 to June 30, 2008. All patients attending the Contact Allergy Unit at the Dermatology department, K.U. Leuven, were patch tested with a baseline series containing tixocortol pivalate and budesonide (22), to which hydrocor- tisone 17-butyrate and prednisone caproate, both diluted to 0.1% in ethanol, were added. Those patients having been exposed to corticosteroids