To investigate whether our hypothesis that cat and dog owners bring allergens to public areas in their clothes was true or not, we studied the levels of Fel d1, Can f1, Der p1 and Der f1 in dust from the clothes and classrooms of children in a Swedish school. We also investigated the levels of allergen in different areas in the four classrooms used by the children. Thirty-one children were selected in four classes, forming three groups: cat owners, dog owners and children without a cat or dog at home. Furthermore, a group of children with asthma was included. Cat and dog allergens were detected in all 57 samples from clothes and classrooms. Mite allergen Der f1 was detected in low concentrations in 6 out of 48 and Der p1 in 5 out of 46 samples investigated. The concentrations of Can f1 were higher than those of Fel d1 in samples from clothes (geometric mean: 2676 ng/g fine dust and 444 ng/g) and classrooms (Can f1: 1092 ng/g, Fel d1: 240 ng/g). The dog owners had significantly higher concentrations of Can f1 (8434 ng/g fine dust) in their clothes than cat owners (1629 ng/g, p < 0.01), children without cat or dog (2742 ng/g, p < 0.05) and children with asthma (1518 ng/g, p < 0001). The cat owners did not have significantly higher levels of Fel d1 (1105 ng/g) in their clothes compared to the other three groups. (D: 247 ng/g, nCnD: 418 ng/g) but the levels were significantly higher than for all children without a cat at home (345 ng/g, p < 0.05). No concentrations of mite allergen and low concentrations of Fel d1 and Can f1 were found in the children's hair. There were significantly higher concentrations of Fel d1 and Can f1 in dust from curtains than in samples from floors and bookshelves (p < 0.05). There was no significant difference between the allergen concentrations in samples from curtains and from desks and chairs, including the teachers' chairs, the only upholstered furniture in the rooms. Our results support the hypothesis that cat and dog owners bring allergens to public areas in their clothes and support other studies showing that textiles and upholstered furniture function as reservoirs of cat and dog allergens. Thus, children with asthma and other allergic diseases will be exposed to cat and dog allergens at school and by contact with pet owners, even if they avoid animal allergens at home.