Background: European studies document that occupational contact dermatitis (CD) is common in hairdressers, but studies from North America are lacking. Objectives: The objectives of this study were to estimate the prevalence of occupational CD among North American hairdressers/cosmetologists (HD/CS) and to characterize responsible allergens and irritants as well as their sources. Methods: A cross-sectional analysis of patients patch tested by the North American Contact Dermatitis Group between 1994 and 2010 was conducted. Results: Of 35,842 patients, 432 (1.2%) were HD/CS. Significantly, most of the HD/CS were female (89.8%) and younger than 40 years (55.6%) as compared with nonYhairdressers (P G 0.0001). The rates for allergic and irritant CD in HD/CS were 72.7% and 37.0%, respectively. The most common body site of involvement was the hand, and this was significantly more common than in non-HD/CS (P G 0.0001). The most frequent currently relevant and occupationally related allergens were glyceryl thioglycolate, p-phenylenediamine, nickel sulfate, 2-hydroxyethyl methacrylate, and quaternium-15. Hair dyes, permanent wave solutions, and other hair products were common sources of allergens. The North American Contact Dermatitis Group allergen series missed at least 1 occupationally-related allergen in 26.2% of patients. Conclusions: Contact dermatitis in North American HD/CS is common, and occupationally related allergens are those found in HD/CS products. Supplemental hairdressing/ cosmetology antigen series are important in detecting all occupationally related allergens in this population.