What is it?
Allergic rhinitis is a group of allergy symptoms affecting the nasal airways. Such symptoms are caused by inhaling airborne particles (allergens) that provoke an inflammatory response of the nasal cavities.
Symptoms
Though nasal symptoms are most commonly associated with allergic rhinitis, patients also often experience symptoms related to the eyes, throat and ears; sleep patterns may also be disrupted. It is therefore important that the patient be made aware of the wide array of symptoms so that they are aware of whether their own symptoms are as a result of an allergy.
Nose: runny and/or itchy nose, nasal congestion, sneezing, loss of taste, facial pressure or pain.
Eyes: itchy and/or red eyes, swelling and blueness of the skin below the eyes.
Throat and ears: Sore throat, hoarse voice, sensation of plugged ears.
Sleep: mouth breathing, frequently disrupted sleep, daytime fatigue.
In severe allergic reactions, sufferers may experience high fever, difficulty breathing, uncontrolled bleeding, and severe earache. In such cases, immediate medical attention should be sought.
Causes
Seasonal allergic rhinitis (commonly known as hay fever) is caused by seasonal outdoor allergens (such as pollen or fungal spores). Perennial allergic rhinitis is caused by indoor allergens that are prevalent throughout the year (such as dust, mould, or animal dander). Symptoms occur year round and worsen during hay fever seasons. Perennial allergic rhinitis tends to be more difficult to treat.
Diagnosis
Diagnosis of allergic rhinitis is based on a physical examination of the presence and severity of the symptoms listed above. Subsequent allergy testing may help identify specific allergens that trigger reactions. Skin testing in the most common method used to determine allergic rhinitis allergens, though blood tests may also be conducted on the recommendation of your doctor.
Sources: http://www.nlm.nih.gov/medlineplus/ency/article/000813.htm