OBJECTIVE: Indoor pets are one source of potential allergens. Several studies reported protective effects of pets’ exposure toward allergy. However, several other studies reported pets’ exposure as risk factor toward allergy. Burden of allergy can be measured by assessing allergic multimorbidity, which is coexistence of two or more allergic diseases. The effect of indoor pets’ exposure toward allergic multimorbidity is still controversial. 
METHOD: The study design was a cross sectional study of 408 children aged 2-12 years at Yogyakarta. We conducted interview to ask whether there were dogs, cats, or birds inside subjects’ house and used ISAAC Questionnaire to find out whether the subjects had asthma, atopic dermatitis, or allergic rhinitis. Mann-Whitney test was used to evaluate the correlation between pets’ exposures and number of allergic diseases.
RESULT: From 408 subjects, 73 subjects (17.9%) lived with indoor pets, which consisted of 16 subjects had dogs (3.9%), 51 subjects had cats (12.5%), and 11 subjects had birds (2.7%). There were 135 subjects without allergic disease (33.1%), 144 subjects with single allergic morbidity (35.3%), and 129 subjects with allergic multimorbidity (31.6%). There was correlation between indoor pets or owning birds and number of allergic diseases (p = 0.006 and p = 0.003, respectively). There was no correlation between owning cats or dogs and number of allergic diseases (p = 0.132 and p = 0.250, respectively).
CONCLUSION: Allergic multimorbidity is related to indoor pets’ exposure and birds’ exposure, but not related to cats’ exposure or dogs’ exposure. Therefore, limiting indoor pets’ exposure, especially birds, toward children may be beneficial in preventing allergic multimorbidity.