My 5 year old son does not have asthma, no wheezing or tightness of chest, but has the asthma like cough. Pediatrician prescribed nebulizer treatment of Albuterol, and inhaler pump of Florent. He just did a treatment, and is still coughing non stop, can I give him some Benadryl as a cough suppressant and to help him sleep, even after the Albuterol treatment?