What you need to do, especially when you feel a cold or the flu coming on, but afterwards too, is take vitamin D. There's a wealth of scientific support showing that it provides unrivalled support for the immune system. It does what we've always been told vitamin C does, without any solid proof. It fights colds without a doubt. It ramps up the body's immune system. It modulates gene expression to release virus-killing compounds called antimicrobial peptides. But you need to take 5-10 times the RDA to get the benefit, 5,000 IU or higher daily virtually eliminates virus infections.
Also, aged garlic extract. 3500 mg a day. You want to saturate your body with it. But eat afterwards or you can get heartburn. Garlic has direct virus-killing effects.
Zinc lozenges- suck on them throughout the day. Zinc has been shown to inhibit the ability of cold viruses to latch onto cells.
melatonin- your body produces this naturally and it helps facilitate a deep sleep. It also induces a powerful immune response. Take at bedtime 10-50 mg.
lactoferrin- this boosts killer cell activity and is a natural constituent of mother's milk. 1,000 mg a day.
You should take these in addition to the high-nutrient supplements you should be taking every day. Any of them will make a difference, but combined, viruses haven't got a chance.
I never get a cold. The most that ever happens is my lips start getting dry. That's when I know I've been exposed to a cold or flu virus and it's trying to take hold, because that's what used to happen before I would come down with full-blown cold symptoms. Now I just take the above and my dry lips are gone by the next day and no other symptoms come. Viruses don't cause colds. A weak immune response causes them.