What are the signs and symptoms of each one?
The signs that are common to the two are runny nose and nasal congestion. More particular to allergies are the itchy, watery eyes and/or throat and the clear, runny nose. With colds you are more likely to have a fever, and maybe some sinus pain. Also the mucus discharge may be a different color, like green or yellow.
How can a person tell the difference?
It's difficult. But if you're getting a cold at the same time every year, or after you visit your cousin who has a cat, and get symptoms, you might have an allergy. There are also some other telltale signs of having an allergy, like eczema, itchy skin, asthma or a history of allergies in the family. A cold usually follows a time course of about 7 to 10 days, usually with a predictable series of symptoms. But it is possible that they have identical symptoms.
How does a doctor tell them apart?
Using good detective work, but sometimes it's trial and error. If the person's coming back to the doctor again and again and the cold remedies aren't working, a doctor will begin to suspect it's an allergy.
What are the treatment options for a cold?
Doctors don't have a cure for the cold, so the treatment options are limited to treating the symptoms. For the congestion there are decongestants. For runny nose there are antihistamines. Cough suppressants can help with a cough.
What are the treatment options for allergies?
Before any kind of medical treatment, it's best to try to modify your lifestyle to avoid what is causing your allergies. For example, if you're allergic to cats, try to avoid them.