1 | Parental smoking and exposure to wood smoke |
2. | Upper respiratory tract infections (rhinitis, nasopharyngitis). |
3 | Day care attendance |
4 | Familial tendency |
5 | Short duration of breastfeeding and bottle feeding. |
6 | Use of pacifiers and presence of digit sucking |
7 | Overcrowding |
8 | Measles, pertussis, tuberculosis and immunosuppression |
9 | Cleft palate, Down syndrome and other craniofacial defects. |