What is rhinitis?
Rhinitis is the term for inflammation of the lining of the nasal passages. This epithelial lining contains hairs to filter incoming air, produces mucus to trap dust and dirt and has sensory receptors which can trigger the sneeze reflex to expel any irritants.
When inflamed or irritated, it triggers a number of symptoms in the nose and surrounding structures including :
Associated symptoms include watery and itchy eyes (often with redness), diminished sense of smell, throat, sinus and/or ear symptoms may also be present to varying degrees
Rhinitis is the most common nasal disorder and is often due to infections in acute rhinitis, while chronic rhinitis is usually a result of allergies.
Types of Rhinitis
Rhinitis can be broadly divided into allergic and non-allergic rhinitis.
- Allergic rhinitis
- Non-allergic rhinitis, which can be subdivided into :
- Non-allergic rhinitis with eosinophilia syndrome (NARES)
Since infectious rhinitis is one of the two most common causes of rhinitis, along with allergic rhinitis, it is often considered separately. All the other causes of non-allergic rhinitis are termed as non-allergic non-infectious rhinitis.
Causes of Rhinitis
The most common causes of both sneezing and a runny nose is an infection or allergy.
Viral upper respiratory tract infections, like a cold or flu (seasonal influenza), are common causes of rhinitis. Apart from the nasal symptoms associated with rhinitis, malaise, fever and a sore throat may also be present . In most cases, rhinitis is temporary and will pass with little or no treatment (acute).
Bacterial infections or fungal infections are also a possibility and may follow a viral respiratory tract. Some of the more common bacteria involved includes the streptococcal, staphylococcal and pneumococcal species. With a fungal infection, it is more likely to occur as an opportunistic infection in HIV or other causes of immune deficiency (mucormycosis). These pathogens are also more likely to target the paranasal sinuses where it can establish itself and multiply within the cavity and result in a prolonged infection.
Rhinitis may also be seen in other infections like :
- Childhood diseases
- Infectious mononucleosis
- Acute or chronic sinusitis
- Respiratory syncytial virus (RSV)
- Whooping cough
Less frequently, other infections may involve the nasal passage like in syphilis and tuberculosis.
The discharge in infectious rhinitis may vary from clear to white-yellow, watery to thick in consistency although severe and prolonged infections may present with yellow or green mucus.
Allergic rhinitis is the most common non-infectious cause of persistent or recurrent rhinitis. It is an immune-mediated hypersensitivity reaction where the inflammatory process is triggered by exposure to substances that are not noxious. It is more frequently seen in people with a history of allergic conditions, like asthma or eczema. Family history is a strong risk factor indicating a genetic cause in many instances.
The rhinitis symptoms tend to aggravate towards the evening and first thing in the morning upon waking, but can persist throughout the day. Known allergens like pollen, house dust mite and animal hair (dander) are common in adults, while food allergies, especially to milk and dairy products, is often seen in children.
Allergic rhinitis can be categorized as :
- Seasonal allergic rhinitis occurs in certain seasons and often related to high pollen and spore counts during certain times of the year.
- Perennial allergic rhinitis persists throughout the year or for most of the year and is often associated with house dust mite and animal dander. It may aggravate seasonally.
Non-Allergic Non-Infectious Rhinitis
Not all the causes of non-allergic non-infectious rhinitis discussed below are grouped according to the sub-categories of non-allergic non-infectious rhinitis.
Environmental airborne irritants often trigger acute rhinitis and passes shortly after removing the trigger factors. This may be seen with :
- Smoke – cigarette, fires
- Industrial pollution , smog
- Strong odors – perfumes
- Certain gases – ammonia, chlorine, hydrogen sulfide.
Cold air, dry environments and air conditioning are other known environmental triggers although it is not due to irritants. These environmental triggers are usually associated with a change in blood flow in the nasal lining. This may be linked to parasympathetic stimulation and is known as vasomotor rhinitis.
Inhalation of organic and non-organic dusts and other airborne irritants may be seen in occupational rhinitis.
Foods, usually hot and spicy foods, may trigger rhinitis. This is known as gustatory rhinitis and is temporary, passing within a few minutes to a few hours.
Hormonal rhinitis is frequently seen with fluctuations in the female hormones in particular. Women with a history of allergic rhinitis tend to find that the condition aggravates throughout pregnancy and with the use of hormone contraceptives. Other pregnant women, with no history of immune-mediated hypersensitivity, may experience rhinitis from the second trimester onwards. It also occurs with other endocrine disorders like hypothyroidism.
Rebound rhinitis is a result of long term and excessive use of decongestants and nasal corticosteroid sprays which were initially prescribed for a chronic runny nose, sneezing and nasal congestion. Discontinuing these medicines will result in a temporary aggravation of the symptoms, which is often reported to be worse that the original presentation before starting the medication.
Drug-induced causes (iatrogenic) of rhinitis is a result of taking certain medication. This may be seen with the use of drugs for hypertension, anti-inflammatories, erectile dysfunction and anxiety. It is more likely to occur in a person with a previous history of rhinitis and may persist for short periods after stopping the medication.
Foreign bodies lodged in the nasal passages may also cause as the lining is irritated by this object and attempts to expel it. Symptoms are often unilateral and a blood-tinged discharge may be noticed. The presence of a foreign body may also result in a secondary infection, usually bacterial, with a foul smelling discharge. This is more frequently seen in children.
Structural defects and growths may be seen with a deviated septum, nasal and paranasal tumors and nasal polyps. A perforated septum, often linked to vigorous nose picking and cocaine snorting, may also cause rhinitis.
Non-allergic rhinitis with eosinophilia syndrome (NARES) or eosinophilic rhinitis is a type of immune-mediated rhinitis although it is not associated with an allergy. An increased concentration of eosinophils may be present in the nasal lining often mediating the inflammatory response.
Atrophic rhinitis is where the nasal lining shrinks and becomes less vascularized. This is seen with age and diseases like Wegener’s granulomatosis.