Background: Until recently, the standard approach to care for individuals with peanut allergy (PA) was limited to allergen avoidance and treatment of reactions with emergency medicines. Objectives: To assess health-care resource utilization (HRU) and costs associated with PA management under allergen avoidance and to identify risk factors associated with peanut reactions that resulted in inpatient (IP) and/or emergency department (ED) visits. Methods: Privately insured individuals with PA diagnosis codes were identified from a large U.S. administrative claims data base (January 1, 1999, to March 31, 2017). PA-related HRU, indicated by a PA diagnosis and/or diagnostic procedure codes and by epinephrine autoinjectors (EAI) prescription fills in medical and pharmacy claims, respectively, and all-cause costs were described per patient-year (PPY). Risk factors associated with peanut reactions in an IP and/or ED setting were identified by using a multivariable logistic regression model. Results: A total of 86,483 patient-years from 14,136 individuals with PA were included. At the patient-year level, 28.1% were ages 0-3 years, 43.6% were ages 4-11 years, 13.7% were ages 12-17 years, and 14.5% were ages ≥ 18 years; 35.6% had PA-related outpatient visits; 50.6% had EAI fills; and 2.4% had PA-related IP and/or ED visits PPY. Younger individuals had more PA-related outpatient visits and EAI fills, with peak intensive use at ages 4-11 years. The proportion of individuals with PA-related IP and/or ED visits was highest among those aged ≥ 18 years. Mean all-cause costs were $3084 PPY; individuals with PA-related IP and/or ED visits incurred $8902 PPY ($17,451 for those with one or more IP visits). Risk factors associated with peanut reactions that resulted in IP and/or ED visits included young adults (odds ratio [OR] 3.19 [95% confidence interval {CI}, 2.66-3.83]), previous peanut reaction(s) (OR 1.66 [95% CI, 1.23-2.24]), asthma (OR 1.33 [95% CI, 1.18-1.51]), and male sex (OR 1.14 [95% CI, 1.01-1.28]). Conclusion: Individuals with PA and under allergen avoidance had significant HRU that varied across all age groups, with more PA-related outpatient visits during preschool and/or school age and PA-related urgent care among adults. Individuals with previous peanut reaction(s), asthma, and males had a higher risk of peanut reactions that resulted in IP and/or ED visits.