It's Probably a Cold If:
You have a cough, low fever, headache, or mild body aches. There are more than 200 cold viruses, and different viruses cause different symptoms. Even so, coughing, a fever, and achiness aren't problems you usually see with allergies. The exception to the rule: Allergies can sometimes trigger a cough from post-nasal drip or if you have asthma.
Your symptoms change every few days. You may start out with a fever and stuffy nose, then have a sore throat for a few days, or get a cough or sinus pain before getting better.
Your mucus becomes yellow, green, or thick. As immune cells fight back against the cold virus, they can make your mucus discolored or thick.
Call Your Doctor If:
You think you have allergies. Talk to your doctor about treatments. She may recommend you see an allergist to have skin testing. That involves putting allergens on your skin to see if they cause a reaction. When you know what you're allergic to, it's easier to avoid it or prepare for a situation where you'll be exposed to it.
But see a doctor right away if you're having trouble breathing, have a skin rash, or have swelling in your mouth. These things can be signs of a severe allergic reaction, and you may need immediate medical help.
You have a fever over 101 F. That can be a symptom of the flu or another infection. You may need prescription medication.
Your cold symptoms get worse over time or don't clear up after 10 days. Though drinking lots of fluids and taking over-the-counter medications can make you more comfortable, there's no cure for a cold. It gets better on its own. If yours lingers, or your symptoms become severe -- for example, your sore throat becomes so painful that you can't swallow -- go to the doctor to get checked out. You could have a more serious problem, like strep or pneumonia.