I use a nebulizer anytime my child gets a cold or a cough. is this advisable? will it bring health issues in the future?

It should not : bring any health issues if used properly for asthma / reactive airway disease which are triggered by cold virus , allergies etc. A lot of times parents misuse it for just a cough and cold! Your child needs to be followed on a regular basis anyway if indeed diagnosed with asthma . Length of treatment, frequency, concerns regarding meds prescribed can then be addressed at your visits .