Hello and hope you are doing well.
Sinecoid is a cough suppressant, so it should be used for dry cough only. It can be used in Asthma, as it reduces air way resistance also. But if you are allergic to the medication, it is best avoided.
Hope this helped and do keep us posted.
It's best to ask a pharmacist. My husband has asthma and he is limited to what he can take for OTC meds. Out pharmacist said there are a few things which he should not take for sinus problems as they will make the asthma worse...because they actually thicken the mucus which makes breathing that much more difficult.