Frequent colds

Hi and thanks for taking the question.
My problem is frequent colds. I get a cold that lasts a week, there is a week or two-week long break and then I get another cold. I've had three so far this fall, one followed by an ear infection.
I have a chronic dry cough, my temperature is usually around 99.5,  but the worst part of all this is the runny nose. The discharge is clear and there is an awful lot of it. I've been taking sudafed but it helps only a little. Tried antihistamine medication for a few days it it made me very drowsy.
My question is: do you think that my colds could be caused by an alergy (allergy) (I've never had any alergies (allergies) before) and what I can do to get rid of them. I'm a teacher and these recurring colds are a great nuisance.

[National Jewish]

Sinusitis is an inflammation of the mucous membranes that line the sinus cavities.  Inflammation of the sinuses could be due to an allergy, an infection, or ongoing exposure to an irritant, such as pollution or smoke.  Symptoms can include a headache or pressure in the area of the sinuses, a runny nose, a stuffy nose, achy teeth, an odor coming from the nose, postnasal drip, cough, sore throat, laryngitis, lightheadedness, constant low fever, and thick, yellow to green nasal drainage.

The best way to identify a sinus infection is with a sinus CT scan, although sinus x-rays are a decent alternative.  A sinus CT scan will also identify if any of the openings that drain your sinuses are blocked.  If your symptoms are due to sinusitis, they will last as long as the inflammation continues.  Here are some ways to clear up the inflammation.  Please check with your doctor to see which of these would work best for you.  Please read our Sinusitis MedFact at http://www.nationaljewish.org/medfacts/sin.html for more information.

The most common cause of sinusitis is an infection, especially when the discharge is green.  Sinus infections can be difficult to treat since they respond slowly.  When any of the openings that drain your sinuses are blocked it will take longer to clear a sinus infection.  If a viral infection is the cause it