Garlic/allicin is amazing. I chew a clove or two if I feel a cold coming on, and it usually knocks it right out.
Apparently, it has the ability to permeate phospholipid bilayers such as those that envelop viruses.
https://www.ncbi.nlm.nih.gov/pubmed/10631291
BHT does as well, its a strong antioxidant you can get in capsules too.
Do you get the allicin max product? thats the onen i know of/use.