Sinus Infection (Sinusitis): Symptoms, Causes and When Antibiotics Help

Acute sinusitis is inflammation of the air-filled spaces around the nose, usually after a viral cold. Congestion, facial pressure, reduced smell, and coloured discharge can feel bacterial, but most cases improve without antibiotics. A bacterial cause becomes more likely when symptoms persist without improvement, are severe, or worsen again after beginning to recover.

What sinusitis is

The sinuses are air-filled spaces in the face that drain through small openings into the nose. A viral upper-respiratory infection can swell the lining, narrow drainage, and trap mucus. Allergy, smoke exposure, polyps, a deviated septum, dental disease, and immune problems can increase risk or prolong symptoms.

“Rhinosinusitis” emphasizes that the nose and sinuses are inflamed together. Acute disease lasts a short period and commonly follows a cold. Recurrent acute sinusitis means separate episodes with recovery between them. Chronic rhinosinusitis involves symptoms for at least 12 weeks and requires a different assessment; repeated antibiotics are not a substitute for confirming inflammation and looking for underlying factors.

Common symptoms

Symptoms can include a blocked or runny nose, facial pain or pressure, reduced smell, post-nasal drip, cough, headache, sore throat, upper-tooth discomfort, bad breath, and fatigue. Children may show daytime cough, nasal discharge, irritability, or poor sleep.

Pain location does not identify a specific sinus reliably. A “sinus headache” may be migraine, particularly when there is nausea, light or sound sensitivity, or disabling attacks without clear nasal inflammation. Upper-tooth infection can produce one-sided facial pain and foul drainage and needs dental assessment.

Viral or bacterial?

There is no perfect symptom-based test. Clinicians use the course and severity to estimate probability. A typical viral cold begins to improve within several days even if congestion and cough linger. Mucus colour changes as immune cells and proteins accumulate and is not a bacterial test.

Three patterns raise concern for acute bacterial rhinosinusitis:

• Persistent: nasal discharge or congestion with facial pressure or cough lasting at least about 10 days without improvement.
• Double worsening: symptoms begin to improve, then nasal discharge, cough, pain, or fever returns or becomes worse.
• Severe onset: high fever with purulent discharge or marked facial pain for several consecutive days.

These patterns increase probability; they do not guarantee a bacterial cause or automatically require the same treatment. Age, immune status, pregnancy, recent antibiotics, complications, and the reliability of follow-up influence the decision.

When to arrange a clinical review

CDC advises review for severe headache or facial pain, symptoms worsening after improvement, more than 10 days without improvement, fever lasting more than three to four days, or multiple episodes in a year. Seek earlier advice for pregnancy, major immune suppression, cancer treatment, recent facial surgery, or significant chronic disease.

Same-day review is appropriate for marked one-sided swelling, severe dental pain with facial swelling, dehydration, rapidly worsening illness, or severe pain not controlled by usual measures. Use emergency care for the eye, brain, airway, or sepsis signs listed above.

How acute sinusitis is diagnosed

For uncomplicated symptoms, diagnosis is usually based on the history and examination. The clinician examines the nose, throat, ears, teeth, face, eyes, and vital signs and considers migraine, dental infection, allergy, and other causes.

Plain sinus X-rays and routine CT scans are not recommended for uncomplicated acute rhinosinusitis. Imaging cannot reliably prove which cases need antibiotics and exposes the patient to cost and, for CT, radiation. CT or specialist imaging is used when complications, an alternative diagnosis, surgery planning, or chronic disease is being evaluated.

A routine nasal swab samples the front of the nose rather than the infected sinus and may grow colonizing bacteria. Culture is reserved for selected severe, complicated, recurrent, or treatment-resistant cases and is collected using an appropriate method.

Why antibiotics are often not the first step

NICE concludes that acute sinusitis is usually self-limiting and antibiotics make little average difference to symptom duration for most uncomplicated cases. Side effects include nausea, diarrhea, allergy, C. diff infection, and selection of resistant bacteria.

No antibiotic does not mean no care. The plan should cover pain relief, hydration, likely duration, review timing, and red flags. In selected cases, a clinician may offer watchful waiting for a short period or a delayed prescription with precise instructions on when to fill it.

Immediate antibiotic treatment is more likely when someone is systemically very unwell, at high risk of complications, or has a serious bacterial pattern. Choice varies by age, allergy, pregnancy, local resistance, recent antibiotic exposure, kidney or liver function, and national guidance. This page does not name a regimen or dose.

Symptom relief

Pain and fever

A pharmacist can help choose an over-the-counter pain or fever medicine that is safe with pregnancy, kidney disease, ulcers, blood thinners, asthma, and other medicines. Follow the label and avoid taking two combination products containing the same ingredient.

Saline spray or irrigation

Saline may feel soothing, although evidence that it changes the course of acute sinusitis is limited. For any device that sends water into the nose, CDC says to use store-bought distilled or sterile water, or tap water that has been boiled and cooled. Drinking-quality tap water is not necessarily sterile enough for nasal rinsing.

Follow device-cleaning instructions, wash and dry hands, and do not share equipment. Seek urgent advice for severe headache, fever, vomiting, or confusion after nasal rinsing. Rare but fatal brain infections have occurred after unsafe water entered the nose.

Nasal decongestants

Decongestant sprays can briefly reduce blockage but overuse can cause rebound congestion. In April 2026, the UK MHRA limited specified common spray and drop ingredients to no more than five consecutive days. Follow the local product label because ingredients and rules vary. Check with a pharmacist for children, pregnancy, high blood pressure, heart disease, glaucoma, or interacting medicines.

NICE found insufficient evidence that nasal saline or decongestants relieve acute sinusitis and no supporting evidence for oral decongestants, antihistamines, mucolytics, steam inhalation, or warm face packs in this condition. Steam over a bowl can cause serious burns, especially in children.

Nasal corticosteroids

A clinician may consider a nasal corticosteroid for selected adults and adolescents with longer symptoms or an allergic component. It may improve symptoms without shortening the illness and correct technique matters. People using other steroid medicines need a review of cumulative exposure. This is not the same as using an oral steroid.

If an antibiotic is prescribed

Take it exactly as directed. Do not use leftovers, share it, or add a second antibiotic. Ask what improvement is expected and when. Reassessment is needed if symptoms worsen rapidly, fail to improve as planned, or return; possibilities include resistant bacteria, dental infection, migraine, a complication, or a non-infectious condition.

Contact a clinician for significant diarrhea during or after treatment. Hives, facial swelling, wheeze, throat tightness, or collapse can indicate allergy; breathing difficulty or collapse is an emergency. A recorded intolerance such as nausea is not automatically the same as allergy and should be described accurately.

Recurrent or chronic symptoms

Repeated episodes deserve review of whether each event is truly bacterial and whether allergy, asthma, dental disease, immune problems, smoke exposure, occupational irritants, polyps, or anatomy contributes. Loss of smell, ongoing blockage, and drainage for at least 12 weeks suggests chronic rhinosinusitis, not one prolonged acute infection.

Unilateral symptoms, recurrent nosebleeds, facial numbness, a visible mass, or persistent one-sided ear symptoms need specialist assessment. Most causes are not cancer, but these patterns should not be repeatedly treated online as “sinus infection.”

Questions people often ask

Does green mucus mean the infection is bacterial?

No. Coloured mucus is common in viral illness. The overall timeline, severity, examination, and risk factors matter.

Can sinusitis cause tooth pain?

Yes, upper teeth can ache with sinus pressure. A diseased tooth can also cause sinus symptoms, especially one-sided pain or foul drainage, so dental causes must be considered.

Should I request a CT scan?

Not for routine uncomplicated acute symptoms. Imaging is reserved for complications, alternative diagnoses, chronic disease evaluation, or surgical planning.

Is “double worsening” proof I need antibiotics?

It raises the probability of bacterial infection and supports clinical review. The treatment decision still depends on severity, risk, and local guidance.

Sources and evidence scope

This guide was researched using CDC sinus infection guidance, the 2025 AAO-HNS adult sinusitis guideline update, NICE guideline NG79 (updated May 2026), CDC advice on safe sinus rinsing, the 2026 UK MHRA decongestant warning, and CDC antibiotic-use guidance. Sources were checked on August 21, 2026. Prescribing, product labels, imaging pathways, and referral access vary by country.