The majority of patients presenting allergic rhinitis and asthma are sensitised to several allergens. Dust mites are the chief culprits, with the two most important species in France being Dermatophagoides pteronyssinus and Dermatophagoides farinae. Studies indicate that 50 to 70% of patients are multi-sensitised. However, it is important to distinguish between sensitisation and allergy: "sensitisation" is an exclusively biological phenomenon (positive prick-tests or IgE assays), while the term "allergy" implies the existence of clinical symptoms detectable by precise history taking. Management of dust mite allergies is based upon fastidious elimination of the offending source, suitable symptomatically treatment and allergy immunotherapy (Am, chiefly by the sublingual route (SLIT). Successful elimination of dust mites depends on the degree of patient sensitisation, the extent of exposure to dust mites, the measures taken, and any other allergies and domestic pollutants present. Removal, which is difficult for dust mites, is random in the case of most other allergens (pollens, moulds, cockroaches, etc.). AIT is the only form of treatment able to modify the immune status of allergic individuals and is indicated in cases of poor control of rhinitis and/or asthma by means of global allergen removal or systematic treatments. In multi-allergic patients, where two sources of allergens are required, these may be administered either in parallel (using two allergen preparations) or in a mixture (using a single preparation). When AIT is given in parallel, for example with dust mites and grass pollens, a recommended interval of 30 minutes should be left between the two allergens. Where AIT is performed using a mixture of allergens within a single preparation, it is recommended that the preparation be made up of a 50/50 mixture of mutually compatible allergen sources. The prescription of multiple AIT underlines the importance of the "dilution factor": mixing several allergens reduces the doses of each allergen in keeping with the number of components used. SLIT is currently the reference pathway, and practically the only approach utilised in children because of its ease of use, as well as the absence of pain and of any serious adverse effects. It must be performed using high-quality standardised allergen extracts with particular attention to the clinical relevance of the allergens used, their safety of use and the patient's quality of life.(C) 2017 Elsevier Masson SAS. All rights reserved.