9 month old with asthma

Olivia

Our son has had a chesty cough and wheezing for about 3 weeks. We took him to the doctors two weeks ago and I brought him back today.

She said it is asthma but obviously can't get a definitive diagnosis this young. She gave us an inhaler with mask to use.

We used it for the first time tonight and he's still coughing in his sleep. Is this normal? Does it take a while to start being effective? It's salbutamol