What could be the cause of my persistent flu, cough

Dear doctor, I am Paul I need your help. Since last year, I have been suffering from persistent flu and cough. It has become so recurrent that I heal for only a couple of days before it resurfaces again. What is causing this because sometime back, I used to spend years without falling sick? Is it that my immune system has weaked because I have even tested for HIV/Aids and I am HIV negative. Dear Paul; Is there only flu and cough or even associated fever, difficulty in breathing, swallowing, throat pain, e.t.c? Has there been sweating in the night, loss of appetite or loss of weight over the past few weeks? If the answer to these questions is no, then definitely there is no infection or serious illness involved. Have you been staying or working in the same place or there has been a change in residence or work place, since these symptoms have started? If yes, then these symptoms could be due to allergy. Allergy could be due to anything in or around in the environment. Dust, fungal spores or pollens, chemicals used in cosmetics, toilette products, sprays, food items, e.t.c. are also source of allergy which can manifest as recurrent cold, cough, skin rashes or breathlessness. At times worm infestation in intestines can also lead to recurrent cough and cold. Diabetes can make one more susceptible to infections due to high blood glucose levels. You need to get a complete blood test done, where high eosinophil levels would confirm presence of allergy. Normal blood glucose levels would exclude diabetes. Stool test can reveal any worm infestation. For now, if your work involves exposure to dust, try to keep nose and mouth covered. Inhaling steam 2-3 times daily and drinking hot water can help to minimize the cold and cough. There are various herbal remedies like taking hot tea with honey, drinking decoction with basil leaves, e.t.c. which are beneficial in such cases. Taking antihistaminic drugs like cetrizine or chlorphenaramine for a week or so will minimize the problem.