A cold or the flu starts out as a viral infection, but in some cases a secondary bacterial infection can occur.

The reason you cough is that your body is trying to mobilize mucus and break the secretions up -- your virus load. Fever, too, is part of the body's way of trying to kill viruses. They don't tolerate a high temperature.

The secondary infections are why some people who have a cold and after a couple of days still feel bad so they go to the doctor, the doctor prescribes antibiotics, and then they start feeling better after they take them.

The continuing sinusitis is the reason for the persistent cough in my patient population. You can get a pattern of coughing that is similar to bronchitis that is a result of the low-grade sinusitis.

It is worth trying for someone who is allergic. Some products are over hyped. But one thing I recommend is getting HEPA (high efficiency particulate air) filters. They do decrease the allergens in the air.