Background/Objectives Diaper dermatitis is often caused by irritant contact occurring beneath the diaper of an infant, and it is aggravated by factors such as dampness, friction, urea, and feces. Food-allergic patients are known to exhibit various skin lesions ranging from urticaria to eczema. This study aims to determine the relationship between persistent diaper dermatitis and food allergy. Methods A retrospective chart review was conducted of pediatric patients with a diagnosis of persistent diaper dermatitis between August 2015 and November 2017. Results The study included 157 patients diagnosed with persistent diaper dermatitis (67 male, 72 female; median age: 13 months). Diaper dermatitis was more common and included the whole perineum in children who had multiple food allergies (P = 0.001). In children with multiple food allergies, the course of diaper dermatitis was more severe, and the condition did not respond to topical treatment (P = 0.025). A longer elimination diet was required for patients with Type I reactions and persistent diaper dermatitis (P = 0.018). In patients with Type II and mixed reactions, diaper dermatitis was more diffuse and covered the whole perineum (P = 0.025). In patients with Type II and mixed reactions, diaper dermatitis was more severe and did not respond to topical treatment (P = 0.025). Conclusions Persistent diaper dermatitis lasting longer than a month may be associated with food allergy. The diaper rash may also be the only indicator of the food allergy. Elimination of the responsible food may allow these patients to recover from persistent diaper dermatitis.