Here's a breakdown of which symptoms belong to which ailments.
The Common Cold -- "Cold and allergy can present similarly," says Silvers, so the defining difference is the length: If your congested nose and breathing difficulty last longer than seven to 10 days, it's probably not a cold. Most likely, it's allergies, and needs to be treated with an antihistamine, not a decongestant.
Seasonal Allergies -- If your sinus congestion is accompanied by watery or itchy eyes and it tends to last several weeks, it's may be allergies, says Silvers. The problem is, many often treat their allergies like a cold, with over-the-counter decongestants, which will work in the short run but are not advisable. "When someone is taking a daytime decongestant every day and a nighttime one to sleep, for weeks and weeks, this is not good," she says. Especially when their allergy might be due to an environmental trigger, such as a feather pillow, that could be easily eliminated.
Sinusitis or Chronic Sinusitis -- With sinusitis, the nasal passageways become inflamed and the liter or more of mucus created every day by your body gets backed up in the sinuses. "This is when you get patients complaining of headache, pressure or pain in their face and chronic fatigue," Silvers says.
A headful of mucus is an exhausted head, one that's hard to lift off the pillow and patients can be irritable and fatigued on most days," says Silvers. If you suffer from facial tenderness, pressure or pain, headache behind the eyes and forehead, or loss of taste or smell and fatigue, you may have sinusitis.
If you experience this three or more times a year, you may have chronic sinusitis, like Burley, and should consult with your physician or an ear, nose and throat specialist. What most people don't know, Silvers says, is that you can have sinusitis without having a runny or stuffy nose or difficulty breathing, because the mucus is congested further back in the sinuses.
If you suffer from any of the above symptoms and they do not resolve within a week or so (and hence are unlikely to be a cold or flu), you should consider seeing your physician, who may refer you to an allergist or an ear, nose and throat specialist.