Sinus infection happens when fluid builds up in the sinuses (air-filled pockets in the face), promoting the growth of germs. It is most commonly caused by a cold and can also be caused by allergies. Symptoms include facial pressure, fever, nasal congestion, and postnasal drip.
Sinusitis falls under theEar, Nose & Throatcategory.
Sinusitis is the inflammation of the air cavities inside the skull (sinuses), usually due to a virus or a bacterial infection. Acute sinusitis is often caused by the common cold virus and normally goes away on its own in less than 4 weeks. Viral sinusitis is one of the most common reasons for improper prescription of antibiotics. Chronic sinusitis lasts for longer than 8 weeks and affects up to 12% of the general population.
Common symptoms of sinusitis include nasal blockage, congestion, discolored nasal discharge, facial tenderness/pain, reduced sense of smell, cough, fever, toothache, and bad breath. Viral sinusitis from the common cold typically resolves in 7-10 days. Bacterial sinusitis may be suspected when symptoms are severe, last more than 10 days without improvement, or worsen after starting to improve initially.
Uncomplicated sinusitis is diagnosed by clinical presentation. Major factors to indicate sinusitis include facial pain, nasal congestion, nasal blockage, discolored mucus, loss of smell, and fever. Minor factors that indicate sinusitis include headache, bad breath, tooth pain, ear pain, fatigue, cough, and otalgia (earache). Additional testing (e.g., cultures) and imaging (e.g., computed tomography) may be done if a bacterial or fungal infection or a chronic or complex disease is suspected. 
Common medical treatments for sinusitis are for symptom relief. Nasal irrigation with saline water is commonly used to reduce nasal congestion and help clear mucus. Also, for reducing congestion, nasal sprays such as oxymetazoline (which should not be used for more than 3 days to avoid rebound congestion) or oral pills such as pseudoephedrine may be used. Antihistamines (diphenhydramine, cetirizine, loratadine, etc.) are not beneficial in viral or bacterial sinusitis, but can help in allergic sinusitis (allergic rhinitis). Topical steroid sprays are best left for chronic and allergic sinusitis. Antibiotics (e.g., amoxicillin-clavulanate) are used sparingly due to concerns of resistance, but can alleviate bacterial sinusitis which does not improve after watchful waiting.
European guidelines hold that supplements with some benefit for the common cold can also be tried for acute sinusitis, for example zinc, vitamin C, and probiotics. Other supplements with limited evidence for improving sinusitis symptoms include umckaloabo (Pelargonium sidoides), bromelain (pineapple enzyme), cod liver oil, horseradish root, and andrographis.  Combination herbal products, often containing Flos magnoliae and Siberian cocklebur fruit, have been studied in China and Taiwan, showing benefit for sinusitis symptoms. However, the generalizability of these results to other geographic locations is unknown.
Specific dietary modifications have not been studied for sinusitis. However, some researchers propose that increasing foods high in polyphenols, such as ginger and green tea, may reduce inflammation and mucus production and therefore moderate symptoms in sinusitis. Following an anti-inflammatory diet, and avoiding refined sugars and processed foods (high in artificial colors, preservatives, histamine) may be helpful, as they may increase inflammation and exacerbate sinusitis symptoms. Also, because milk allergy is common in chronic sinusitis, its intake can worsen symptoms in some people.
Regular exercise, stress management, adequate hydration, good sleep quality and avoidance of environmental toxins (pollution, smoke, etc.) are lifestyle modifications that may help to prevent sinusitis. Also, acupressure and acupuncture have been used to alleviate sinusitis-related symptoms such as facial pain. Although nasal washes with saline are most common, nasal washes containing manuka honey or the herb Cyclamen europaeum have also been studied, but did not seem promising.
The common cold virus is the most common cause of acute sinusitis. Bacterial sinusitis is usually caused by Haemophilus influenzae, and less commonly by Streptococcus pneumoniae, Staphylococcus aureus, Streptococcus pyogenes, or anaerobic bacteria. Chronic sinusitis is most commonly caused by Staphylococcus aureus or multiple bacteria, while fungal sinusitis is most commonly seen in immunocompromised patients and caused by Aspergillus. Physiologically, sinusitis develops when clearance of mucus is impaired and and the nasal cavity is abnormal or not functioning properly.
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