Common after a cold or flu, blocked nose, reduced smell, green or yellowish mucus discharge from the nose, pain, swelling, tenderness around eyes, cheeks, or forehead. Sinusitis, also known as rhinosinusitis, is an inflammation of the sinuses. The sinuses are air-filled spaces located behind the cheekbones, forehead, and eyes. When the sinuses become inflamed, they can become swollen and blocked with mucus, leading to pain, pressure, and congestion.   

Causes of Sinusitis:

• Viral infections: Common cold viruses are the most frequent cause of sinusitis.
• Bacterial infections: Bacteria, such as Streptococcus pneumoniae and Haemophilus influenzae, can also cause sinusitis, especially if a viral infection hasn't cleared up.   
• Fungal infections: In some cases, fungi can cause sinusitis, particularly in people with weakened immune systems.   
• Allergies: Allergies to pollen, mold, dust mites, or pet dander can trigger inflammation in the sinuses.   
• Structural problems: Nasal polyps or a deviated septum can obstruct sinus drainage and increase the risk of sinusitis.   

Symptoms of Sinusitis:

• Facial pain or pressure
• Stuffy nose
• Nasal congestion
• Postnasal drip
• Thick, colored nasal discharge (yellow or green)   
• Cough
• Fever
• Fatigue
• Headache
• Loss of smell or taste
• Bad breath
• Pain in the teeth or upper jaw