ABSTRACT: Allergen immunotherapy (AIT) can be defined as the repeated administration of specific allergens to patients with IgE-mediated inflammatory diseases, with the ultimate goal of providing protection against allergic symptoms and inflammatory reactions associated with natural exposure to these allergens. Specifically, the therapy primarily strives to establish long-term tolerance against allergens by inducing allergen-specific regulatory B and T cell responses, in addition to modulating the mast cell and basophil activation thresholds to mitigate allergic pathogenesis. AIT is conventionally administered to patients both subcutaneously and sublingually; however, additional routes of administration (ie. intralymphatic immunotherapy) are under investigation. AIT is suitable for both adults and children for a variety of allergens including pollen, pet dander, house dust mite, venom, and a number of food allergens including peanut, egg, and milk. Nevertheless, more research is needed to elucidate many of the direct mechanisms in which AIT suppresses inflammatory immune responses. Reviews The efficacy of peptide immunotherapy for cat-induced respiratory allergy INTRODUCTION Respiratory Allergy Te prevalence of allergic diseases, including but not limited to allergic respiratory diseases, is increasing globally, particularly in developing nations 1 . Allergic respiratory diseases, including rhinitis and asthma, are complex infammatory diseases associated with signifcant quality of life disruption, a decrease in work productivity, missed school, and increased health care costs 2,3 . Allergic rhinitis (AR) is characterized by infammation of the nasal membranes, while allergic asthma (AA) is characterized by infammation of the large airways of the lungs 2,3 . Worldwide, over 400 million people are afected by AR and over 300 million people by AA 1 . According to the World Health Organization, the number of people with AA is expected to rise to 400 million by 20251. Furthermore, there are clear links between the upper and lower airways as AR and AA are frequently comorbid conditions 2,4,5 . More than 80% of patients with AA also have AR, whereas around 40% of patients with AR have asthma comorbidly 5 . Symptoms of AR are mostly nasal and include sneezing, itching, rhinorrhea, and/or nasal congestion 3,6 . In addition, AR is frequently accompanied by symptoms involving the eyes, ears, and throat, including postnasal drainage 3 . AR is often diagnosed clinically through the results of a careful history and physical examination 3 . AR is strongly suspected when two or more symptoms out of watery rhinorrhea, sneezing, nasal obstruction, and nasal pruritus persist for ≥1 hour on most days 6 . Te skin prick test or the serum-specifc immunoglobulin E (IgE) level can be used to confrm the diagnosis 6 . Te frequency of AR increases with age, and other risk factors include positive allergy skin tests, higher socioeconomic class, family history of allergy, and being born during the pollen season 3 . AA is characterized by airway infammation, remodeling, and hyperresponsiveness, and symptoms include shortness of breath, cough, chest tightness, and/or wheezing 2 . AA is often clinically diagnosed through the results of the medical history and physical examination. Te diagnosis is made when the patient reacts positively to a skin prick test and presents with episodic symptoms of airfow obstruction or airway hyperresponsiveness which are partially reversible 2 . Confrmation of diagnosis is often done using spirometry to demonstrate obstruction and assess reversibility, in which reversibility is determined by an increase in forced expiratory volume in 1 second (FEV1) of greater than or equal to 12% from 44 Authors: Jia Lu¹, BHSc(c) Matthew Boroditsky 2 , MD(c) John Paul Oliveria 3,4 , PhD 1. Faculty of Health Sciences, Master University, Hamilton, ON, Canada 2. Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada 3. Department of Medicine, Division of Respirology, McMaster University, Hamilton, ON, Canada 4. School of Medicine, Department of Pathology, Stanford University, Palo Alto, CA, United States VOLUME 15, ISSUE 1 | 2018