Most likely due to a viral illness (most common) followed by bacterial super-infection (bacteria super-infection means when a bacterial infection occurs in setting where viral illness is also present). Less common is bacterial infection alone. A viral component is most likely present if symptoms do improve partially with antibiotics followed by immediate recurrence of symptoms after antibiotics completed resulting in repeated courses of antibiotics. In this scenario, it is best to avoid antibiotics unless the child is quite ill as only time will allow for the viral illness to resolve which is the main problem. Conservative care with saline spray to the nose followed by bulb suctioning is recommended. Daily Xlear Nasal Spray may also be helpful.
This treatment is sometimes used, mainly in cases where symptoms are severe and not helped by other treatments. It is done using a series of injections of the allergen causing the rhinitis, in increasing quantities. The idea is that your immune system will become desensitised to the allergen. This means that the allergic response that your body mounts when it is exposed to the allergen in the future is reduced, so improving your symptoms. Another technique is being developed which involves placing the allergen under the tongue. However, this may not yet be widely available.