Abstract Rationale: Over 50% of U.S. households have a cat or dog, and ∼30% of people experience allergies to these pets. However, limited research examines whether sensitization to cats vs. dogs result in differing markers of asthmatic severity. We hypothesize a significant difference between these groups. Methods: We conducted a retrospective review of asthmatics seen at the Drexel University Severe Asthma Clinics (2008-2019). Patients were separated into two groups: those with a higher allergen-specific IgE to cat vs. dog and vice versa. We also contrasted those sensitized to only cats or only dogs. Sensitizations were identified using the NortheasternU.S. 25 aeroallergens ImmunoCAP™ test. Two-sample unequal variance t-tests compared peripheral blood eosinophil counts (PBEC), total Immunoglobulin E (IgE) levels, and pulmonary function tests (PFTs) between groups. Results: Among 532 asthmatics, 200 (37.6%) were cat-, 190 (35.7%) dog-, 163 (30.6%) dual -, 38 (7.1%) cat mono-, and 27 (5.1%) dog mono-sensitized. 161 (30.3%) showed higher sensitization to cats, 63 (11.8%) to dogs, 5 had equal sensitization, and 303 (57%) were not sensitized to either. No significant differences were found between those with higher cat or dog sensitization in PBEC (p=0.17), total IgE (p=0.06) levels, forced expiratory volume in one second (p=0.70), FEV1/forced vital capacity (p=0.46), forced expiratory flow (p=0.92), residual volume/total lung capacity (p=0.33), or diffusing capacity (p=0.48). Mono-sensitized individuals also showed no significant differences. Conclusion: In an urban cat- and/or dog-sensitized moderate to severe asthma cohort, we found that cat sensitization was 2.5x more common than dog sensitization. There were no significant differences comparing the cat or dog predominant dual- or mono-sensitized groups in asthma severity markers (PBECs, total IgE, PFTs). Our data suggest that clinicians should recommend similar avoidance strategies for patients sensitized to either pet.