Thank you for your query,
Is there any family history of asthma?
Your child seems to have hyper reactive airway disease
could be asthma.
As your child has been on nebulization with duolin and not showed a response, a steroid may help to relive the wheezing
in addition to the bronchodilator
But your child should be in regular follow up with the Pediatrician
to assess his severity, symptoms and to plan the appropriate management.
Avoid exposure to cold air, dust,smoke , plants, pollen and animals.
Hope I have answered your query.