What is the Difference Between Allergies and a Sinus Infection?
Medically reviewed by Andre Stone | MD, University of Pittsburgh School of Medicine on August 25th, 2026.
Allergies and sinus infections differ primarily in their cause and duration. Allergies result from your immune system overreacting to harmless substances like pollen or dust, causing symptoms that persist as long as you're exposed to the trigger. Sinus infections, also called sinusitis, are usually caused by viruses and can sometimes be caused by bacteria; fungal sinusitis is uncommon. Acute symptoms often improve within about 7-10 days, while symptoms that last longer, worsen after improving, or are severe may need medical evaluation. Allergic symptoms include clear nasal discharge, sneezing, and itchy eyes that worsen seasonally. Sinus infections can cause thick nasal mucus, congestion, facial pain, and pressure around the cheeks or forehead. Mucus may be clear or colored, and its color alone does not show whether an infection is bacterial. Allergies do not usually cause fever. A fever can occur with sinusitis, particularly in some severe bacterial cases, but many sinus infections cause no fever.
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