My wife has mild asthma, but with a history of chronic bronchial ...

My wife has mild asthma, but with a history of chronic bronchial problems: whenever she has a "cold" the accompanying cough goes on for weeks, and she is unable to bring up her secretions. For several months she has taken Singulair on a daily basis, as prescribed by her allergist. This, along with occasional Alupent, has kept her asthma in check. But with the current viral URI, her throat has been "tight" and sore for a period much longer than one might expect, and her cough has gone on for three weeks. There doesn't seem to be a bacterial component here, which would indicate using an antibiotic; it is mostly the irritation of her throat, and the constant cough that's a problem. Anyone else using Singulair have this happening? The side effects given on the stuffer are so broad that they're difficult to interpret.