I think I may be able to add a bit to this thread.
Growing up I was always the "sick kid" any sneeze that comes my way, bam I got it. Forgetting to wash my hands before a meal? Got sick. Everyone would wonder whats wrong with me. I litterally would get sick, recover, and about 3 weeks later, get sick again. Almost never bacterial, always viral. Running noses, flu etc.
When I got sick, it wouldnt be the 3 day sniffles. I would go thru at least 3 big tissue boxes, with bloody sore nose, and about 2-3 week long intense colds.
In time, and desperation it was ruining my education, work, life.. I started to research what I can do. And now I must say, I get sick once in a blue moon. Last winter for the first time ever I did not get sick ONCE.
These are the things I take regularly and I really cannot believe this all works, but its undeniable with me, and now everyone who knows me.
Elderberry (Sambucus) 1 Teaspoon a day. AMAZING anti-viral
Olive Leaf Powder from Olivus (Not olive leaf extract as it doesnt have all the balanced constituents. Olive leaf is one of the most amazing things for viruses. It kills almost all viruses that are put against it in testing. (There can be a herxheimer reaction with so much pathogens being killed off, so becareful) I take 1 tablespoon every day.
Beta-1,3-Glucan (like epicor someone stated) It has the ability to increase white blood cell count, and increase the FUNCTION of the immune system. Macrophages are far more active. Attaches to them at their receptors signaling them to increase function and speed. Very interesting stuff. I take 500mg every day
Mushroom Extract with Reishi, shiitake, maitake and cordyceps are amazing at increasing T cells and immune function. I take 1 pill every day
Vitamin D. If you notice in northern America many flues start at the end of August, there is some studies on Vitamin D and its role in keeping flues at bay. After August, the sun shifts its angle, and our bodies do not produce adequate vitamin D at this time, due to inadequate UV. (Try to get sunlight between 10am and 2pm as the Sun angle is perfect for producing maximal vitamin D. This has been linked to flues acting up again, as viruses act in a cyclical fashion. I take 5000iu every day, especially after August.
Coconut Oil. Has lauric acid in it, infact a product called Lauricidin is an extract from this. Lauric acid is found in mothers milk as well and plays a big role in immunity. It actually helps liquify the shield around viruses, leaving them susceptible to our immune systems. (virus uses the fats to make its lipid layer, since lauric acid will not properly function in the lipid layer, the virus's protection disintegrates. I take two tablespoons every day.
Vira-Stop. Proteolyitic Enzymes. Some viruses have capsids around them, which are protein shields (basically). Vira-stop can go in and destroy those shields. I dont take this anymore due to price, but have before with great effects.
Oil of Oregano. VERY VERY POWERFUL STUFF. I have a nasal inhaler with oregano in it, I take oregano drops every day, and also oregano gel caps once a day. Everytime I feel a sniffle coming along, I take a sniff of my nasal spray and I dont get sick. It litterally destroys any bacteria, fungus, virus that comes in contact with it. Nothing can survive in my sinuses (where most common colds initiate viral replication.
And lastly for therapeutic reasons, I use aromatherapy from a nebulizer. I do this for fun, and it relaxes me. It has oregano oil in it, eucalpytus, ravensara, hyssop, Lime oil, and a few others. This goes from my nasal.. sinusus, into throat, and down into lungs. Helped me get over pneumonia once very fast. I do not actually get sick anymore, and when I do, its usually done in a day or two.
And I cannot forget garlic, 1 clove a day with food!
Hope this helps