Hello, Azithromycin is a good choice of drug and 500mg od (or 250mg twice daily) for 5 days is sufficient. However, you must remember that a one-off course of antibiotics may not do any harm but if you need antibiotics again, do consult your doctor to see if this is really required. Allergies can feel like a constant flu infection, and testing is recommended. You may already have had tests but skin prick testing or specific IgE blood test for house dust mite, animal dander, molds (alternaria, aspergillus, cladosporium etc) can be difficult to avoid and treat unless you know that these are also problems. Rhinosinusitis or just rhinitis resolves on long acting antihistamines and nasal steroid spray like nasonex taken for 6-8weeks. Thanks.