Both seasonal allergies and sinus infections can make you feel congested and miserable, and sometimes it's difficult to tell them apart. In addition, allergies and sinus infections are linked; nasal blockage caused by allergies can increase risk of sinus infections. But while sinus infections result from blocked mucus becoming infected with bacteria, MayoClinic.com notes that allergies are a result of your immune system reacting to a foreign substance, such as pollen, by releasing histamines. Some key differences between an allergy and a sinus infection can help you distinguish between the two.
Facial Pressure and Pain
The severity of your facial pain, headache and sensation of pressure is probably the most important factor in distinguishing sinus infections from allergies. Allergies usually don't cause nearly as much pain and pressure as sinus infections do. According to Scott Murkin, M.D., a physician at Doctor's Express, an urgent care facility in High Point, North Carolina, you may feel pressure and pain in your nose, cheeks, forehead and even upper teeth when you have a sinus infection. Occasionally, the pain and infection will spread to your inner ear. McKenzie Pediatrics, located in the Springfield-Eugene area of Oregon, reports that the headache of a sinus infection tends to becomes progressively worse over several days. Health.com advises taking over-the-counter decongestants to relieve symptoms but cautions that they should not be used for more than three days because of the risk of worsening congestion and raising blood pressure and heart rate. According to Murkin, if your sinus symptoms last longer than four days, you should see a doctor.
Onset and Duration
Another way to tell the difference between allergies and sinus infections is to note how they develop and how long they last. According to McKenzie Pediatrics, sinus infections don't just suddenly appear out of nowhere; they always follow either allergies or an upper respiratory infection or cold that has been present for at least 10 days. Health.com notes that untreated sinus infections typically last about two weeks. In contrast, Murkin notes that allergies tend to be seasonal; their intensity is affected by the local allergen count.
Fever, Body Aches, Nausea
Another difference between sinus infections and allergies is that only sinus infections cause fever and body aches. With a sinus infection, you may also experience a pronounced lack of appetite or feel nauseated. Murkin adds that in general, you will feel sicker and more fatigued with a sinus infection than you will with seasonal allergies.
An itchy, runny nose and itchy, watery eyes—medically known as conjunctivitis—are an indication of allergic rhinitis, also known as hay fever. They are not a sign of a sinus infection, but if you suffer from allergies, you may have these symptoms along with your sinus symptoms.