I used to take something called Zicam for colds and allergy. It was a minor help at symptoms reduction and severity and length of illness. Here in USA it's an over-the-counter med. It used to contain Zinc and was alleged to reduce length and intensity of the symptoms.
However Zicam has been in trouble with investigation and FDA legal issues and some recalls. Reputation is questionable. See the following link:
Be aware that there is no cure for flu..just get bed rest and lots of fluids.,.preferably hot soups and juices. For reducing congestion. eat or drink no dairy products. Monitor your temps often.