For sinusitis lasting more than 12 weeks a CT scan is recommended. On a CT scan, acute sinus secretions have a radiodensity of 10 to 25 Hounsfield units (HU), but in a more chronic state they become thickened, with a radiodensity of 30 to 60 HU.

Nasal endoscopy and clinical symptoms are also used to make a positive diagnosis. A tissue sample for histology and cultures can also be collected and tested. Allergic fungal sinusitis (AFS) is often seen in people with asthma and nasal polyps. In rare cases, sinusoscopy may be made.

Nasal endoscopy involves inserting a flexible fiber-optic tube with a light and camera at its tip into the nose to examine the nasal passages and sinuses. This is generally a completely painless (although uncomfortable) procedure which takes between five and ten minutes to complete.

Health care providers distinguish bacterial and viral sinusitis by watchful waiting. If a person has had sinusitis for fewer than 10 days without the symptoms becoming worse, then the infection is presumed to be viral. When symptoms last more than 10 days or get worse in that time, then the infection is considered bacterial sinusitis. Imaging by either X-ray, CT or MRI is generally not recommended unless complications develop. Pain caused by sinusitis is sometimes confused for pain caused by pulpitis (toothache) of the maxillary teeth, and vice versa. Classically, the increased pain when tilting the head forwards separates sinusitis from pulpitis.

Optical fiber endoscopy can confirm the diagnosis in case of doubt, directly visualizing the inflamed adenoid.

In cases of viral adenoiditis, treatment with analgesics or antipyretics is often sufficient. Bacterial adenoiditis may be treated with antibiotics, such as amoxicillin - clavulanic acid or a cephalosporin. In case of adenoid hypertrophy, adenoidectomy may be performed to remove the adenoid.

It is hard to differentiate a viral and a bacterial cause of a sore throat based on symptoms alone. Thus often a throat swab is done to rule out a bacterial cause.

The modified Centor criteria may be used to determine the management of people with pharyngitis. Based on 5 clinical criteria, it indicates the probability of a streptococcal infection.

One point is given for each of the criteria:

- Absence of a cough

- Swollen and tender cervical lymph nodes

- Temperature >

- Tonsillar exudate or swelling

- Age less than 15 (a point is subtracted if age >44)

The McIsaac criteria adds to the Centor:

- Age less than 15: add one point

- Age greater than 45: subtract one point

The Infectious Disease Society of America however recommends against empirical treatment and considers antibiotics only appropriate following positive testing. Testing is not needed in children under three as both group A strep and rheumatic fever are rare, except if they have a sibling with the disease.

Absolute eosinophil count, nasal smear, skin and in vitro allergy tests to rule out allergic rhinitis, acoustic rhinometry for measuring nasal patency, smell testing, CT scan in cases of sinus disease and MRI in case of mass lesions.

Treatment for fungal sinusitis can include surgical debridement; helps by slowing progression of disease thus allowing time for recovery additionally we see the options below:

- In the case of invasive fungal sinusitis, echinocandins, voriconazole, and amphoterecin (via IV) may be used

- For allergic fungal sinusitis, systemic corticosteroids like prednisolone, methylprednisolone are added for their anti-inflammatory effect, bronchodilators and expectorants help to clear secretions in the sinuses.

In most cases treatment for rhinorrhea is not necessary since it will clear up on its own—especially if it is the symptom of an infection. For general cases blowing your nose can get rid of the mucus buildup. Though blowing may be a quick-fix solution, it would likely proliferate mucosal production in the sinuses, leading to frequent and higher mucus buildups in the nose. Alternatively, saline nasal sprays and vasoconstrictor nasal sprays may also be used, but may become counterproductive after several days of use, causing rhinitis medicamentosa.

In recurring cases, such as those due to allergies, there are medicinal treatments available. For cases caused by histamine buildup, several types of antihistamines can be obtained relatively cheaply from drugstores.

People who prefer to keep clear nasal passages, such as singers, who need a clear nasal passage to perform, may use a technique called "nasal irrigation" to prevent rhinorrhea. Nasal irrigation involves rinsing the nasal cavity regularly with salty water or store bought saline solutions.

There is low or very-low quality evidence that probiotics may be better than placebo in preventing acute URTIs. Vaccination against influenza viruses, adenoviruses, measles, rubella, "Streptococcus pneumoniae", "Haemophilus influenzae", diphtheria, "Bacillus anthracis", and "Bordetella pertussis" may prevent them from infecting the URT or reduce the severity of the infection.

The Centers for Disease Control describe protocol for treating sinusitis while at the same time discouraging overuse of antibiotics:

- Target likely organisms with first-line drugs: Amoxicillin, Amoxicillin/Clavulanate

- Use shortest effective course: Should see improvement in 2–3 days. Continue treatment for 7 days after symptoms improve or resolve (usually a 10–14 day course).

- Consider imaging studies in recurrent or unclear cases: some sinus involvement is frequent early in the course of uncomplicated viral URI

Treatment comprises symptomatic support usually via analgesics for headache, sore throat and muscle aches. Moderate exercise in sedentary subjects with naturally acquired URTI probably does not alter the overall severity and duration of the illness. No randomized trials have been conducted to ascertain benefits of increasing fluid intake.

In terms of diagnosis, the clinical examination gives an idea about fungal sinusitis, as well as:

Nose examination: The mucosa is usually boggy and edematous with clear mucoid secretions. The turbinates are congested and hypertrophic.

Pharynx examination: Mucosal injection and lymphoid hyperplasia involving tonsils, adenoids and base of tongue may be seen.

Gargling salt water is often suggested but evidence looking at its usefulness is lacking. Alternative medicines are promoted and used for the treatment of sore throats. However, they are poorly supported by evidence.

Rhinorrhea can occur as a symptom of opioid withdrawal accompanied by lacrimation. Other causes include cystic fibrosis, whooping cough, nasal tumors, hormonal changes, and cluster headaches. Due to changes in clinical practice, Rhinorrhea is now reported as a frequent side effect of oxygen-intubation during colonoscopy procedures [A simple, innovative way to reduce rhinitis symptoms after sedation during endoscopy" by Nai-Liang Li, et al, Canadian Journal of Gastroenterology, 2011, Feb; volume 25(2): pages 68–72.]. Rhinorrhea can also be the side effect of several genetic disorders, such as primary ciliary dyskinesia.

A 2014 systematic review of clinical trials does not support using routine rapid viral testing to decrease antibiotic use for children in emergency departments. It is unclear if rapid viral testing in the emergency department for children with acute febrile respiratory infections reduces the rates of antibiotic use, blood testing, or urine testing. The relative risk reduction of chest x-ray utilization in children screened with rapid viral testing is 77% compared with controls. In 2013 researchers developed a breath tester that can promptly diagnose lung infections.

Extreme deviation of nasal septum may be accompanied by atrophic rhinitis on the wider side.

First-generation antihistamine has been suggested as first-line therapy to treat post-nasal drip.

Any tooth that is identified, in either the history of pain or base clinical exam, as a source for toothache may undergo further testing for vitality of the dental pulp, infection, fractures, or periodontitis. These tests may include:

- Pulp sensitivity tests, usually carried out with a cotton wool sprayed with ethyl chloride to serve as a cold stimulus, or with an electric pulp tester. The air spray from a three-in-one syringe may also be used to demonstrate areas of dentin hypersensitivity. Heat tests can also be applied with hot Gutta-percha. A healthy tooth will feel the cold but the pain will be mild and disappear once the stimulus is removed. The accuracy of these tests has been reported as 86% for cold testing, 81% for electric pulp testing, and 71% for heat testing. Because of the lack of test sensitivity, a second symptom should be present or a positive test before making a diagnosis.

- Radiographs utilized to find dental caries and bone loss laterally or at the apex.

- Assessment of biting on individual teeth (which sometimes helps to localize the problem) or the separate cusps (may help to detect cracked cusp syndrome).

Less commonly used tests might include trans-illumination (to detect congestion of the maxillary sinus or to highlight a crack in a tooth), dyes (to help visualize a crack), a test cavity, selective anaesthesia and laser doppler flowmetry.

Antibiotics are aimed at gram positive bacteria. Medical attention should be sought if symptoms persist beyond 2–3 days.

CT scan can show the full extent of the polyp, which may not be fully appreciated with physical examination alone. Imaging is also required for planning surgical treatment. On a CT scan, a nasal polyp generally has an attenuation of 10–18 Hounsfield units, which is similar to that of mucus. Nasal polyps may have calcification.

Nasal polyps can be seen on physical examination inside of the nose and are often detected during the evaluation of symptoms. On examination, a polyp will appear as a visible mass in the nostril. Some polyps may be seen with anterior rhinoscopy (looking in the nose with a nasal speculum and a light), but frequently, they are farther back in the nose and must be seen by nasal endoscopy. Nasal endoscopy involves passing a small, rigid camera with a light source into the nose. An image is projected onto a screen in the office so the doctor can examine the nasal passages and sinuses in greater detail. The procedure is not generally painful, but the patient can be given a spray decongestant and local anesthetic to minimize discomfort.

Attempts have been made to develop scoring systems to determine the severity of nasal polyps. Proposed staging systems take into account the extent of polyps seen on endoscopic exam and the number of sinuses affected on CT imaging. This staging system is only partially validated, but in the future, may be useful for communicating the severity of disease, assessing treatment response, and planning treatment.

Normal surgical masks and N95 masks appear equivalent with respect to preventing respiratory infections.

Due to the human ear's function of regulating the pressure within the head region, catarrh blockage may cause discomfort during changes in atmospheric pressure.

Studies have shown that sinusitis is found in about 60% of the cases on the fourth day after the manifestation of sinus. Moreover, patient may be afflicted with an acute sinus disease if OAC is not treated promptly upon detecting clear signs of sinusitis. So, early diagnosis of OAC must be conducted in order to prevent OAF from setting in.

Spontaneous healing of small perforation is expected to begin about 48 hours after tooth extraction and it remains possible during the following two weeks. Patient must consult the dentist as early as possible should a large defect of more than 7mm in diameter or a dogged opening that requires closure is discovered so that appropriate and suitable treatment can be swiftly arranged or referral to Oral Maxillofacial Surgery (OMFS) be made at the local hospital, if required.

A comprehensive preoperative radiographic evaluation is a must as the risk of OAC can increase due to one or more of the following situations :-

- Close relationship between the roots of the maxillary posterior teeth and the sinus floor

- Increased divergence or dilaceration of the roots of the tooth

- Marked pneumatization of the sinus leading to a larger size

- Peri-radicular lesions involving teeth or roots in close association with the sinus floor

Hence, in such cases:

- Avoid using too much of apical pressure during tooth extraction

- Perform surgical extraction with roots sectioning

- Consider referral to OMFS at local hospital

Rhinitis medicamentosa is a form of drug-induced nonallergic rhinitis which is associated with nasal congestion brought on by the use of certain oral medications (primarily sympathomimetic amine and 2-imidazoline derivatives) and topical decongestants (e.g., oxymetazoline, phenylephrine, xylometazoline, and naphazoline nasal sprays) that constrict the blood vessels in the lining of the nose.