Coughs can, of course, be caused by cold or flu infections but if this is not the case with you, the next most likely reason is that you have an air-borne allergy.
Allergies to house dust can cause a condition we call allergic rhinitis.
Other symptoms you might experience include a slight runny nose or sneezing.
If you are badly affected, it may also give rise to slight asthma and shortness of breath – if you are experiencing these symptoms, consult your doctor.
To help yourself, I would suggest that you avoid consuming cow’s milk and dairy produce.
If you would like to use a natural remedy for your problem, you might wish to try Pollinosan, formulated to treat both allergic rhinitis and hayfever.