Acute sinusitis is an acute inflammatory reaction that occurs in the mucous membranes of the sinuses, typically with a sudden onset and lasting for up to four weeks. The sinuses are air-filled cavities within the bones of the face, lined with mucous membranes. When these membranes become infected or irritated by other factors, inflammation occurs. Acute sinusitis is characterized by a short duration and a rapid escalation of symptoms, distinguishing it from chronic sinusitis.

The location of the sinuses can be likened to rooms connected to the nasal cavity, which functions as a corridor. This "corridor" allows for ventilation and drainage. Each side of the face has four sinuses, for a total of eight—four pairs in all. These include the frontal, ethmoid, sphenoid, and maxillary sinuses. These sinuses open into the nasal cavity, just like doors leading from rooms into a hallway. Normally, these passages remain clear, enabling proper airflow and drainage of mucus. However, when the openings of the sinuses become blocked due to infection, allergies, or other factors, secretions cannot drain properly, creating a breeding ground for bacteria or viruses, which leads to inflammation and, in cases of sudden onset, acute sinusitis.

Common causes of acute sinusitis include viral and bacterial infections, allergic reactions, upper respiratory tract infections (such as the common cold), or anatomical abnormalities like a deviated septum. Viral infections are the most frequent cause, especially within a few days of contracting a cold. Bacterial infections may occur if the original viral sinusitis is not adequately treated early on or if the immune system is compromised. Additionally, environmental factors such as pollution, smoke, and dust can increase the risk of developing sinusitis.

Symptoms of acute sinusitis typically include persistent nasal congestion, facial pain or tenderness—especially around the forehead, under the cheekbones, over the bridge of the nose, and around the eyes. Patients may also experience thick yellow or green nasal discharge, reduced sense of smell, headaches, and sometimes fever or general malaise. Symptoms often become more pronounced within a week. If symptoms persist for more than ten days, it may indicate a bacterial infection. Severe cases of acute sinusitis can lead to complications such as ear infections, tooth pain, or, in rare cases, spread to the eye sockets or brain, leading to more serious conditions.

Treatment for acute sinusitis often involves self-care and symptom management. This includes increasing fluid intake, keeping the nasal passages moist, using saline nasal sprays, or employing steam therapy to help relieve nasal congestion. Over-the-counter nasal decongestants or antihistamines can also be used for short-term symptom relief. If a bacterial infection is suspected, a doctor may prescribe antibiotics, but this is only recommended in confirmed cases or when symptoms worsen. In some cases, especially for patients with chronic allergic rhinitis or structural issues such as a deviated septum, further medical intervention or surgery may be required.

Although acute sinusitis is common, early and proper management can effectively reduce the risk of complications and prevent the condition from progressing into chronic sinusitis or other serious issues. If symptoms last for several weeks or are accompanied by severe headaches, changes in vision, or signs of intracranial infection, it is advised to seek immediate medical attention for further diagnosis and treatment.