Recommend. For a cough with allergies, try an antihistamine (zyrtec, claritin, (loratadine) allegra). If your cough persists, you need to try something with dextromethorphan in it - this is specifically a cough suppressant. These products are often named with -dm, such as robitussin-dm, or mucinex-dm.
Treat the problem. For coughs related to allergies, you need to be concerned about the cause. Is it drainage or sub clinical allergic asthma. Need to see your doctor. He/she can easily determine this. Once done, medication is the mainstay of treatment. Singular is my drug of choice for both asthma and allergic rhinitis. However, if medicines fail, you will need to consider allergy testing and shots to desensitize.