Many products, like Airborne, claim to ‘boost your immune system’. These claims are based off of fundamentally inaccurate understandings of the immune system. Your immune system is not like a muscle that you can boost in strength, but is more analogous to a teeter-totter that you want to keep in balance to prevent detrimental affects on either side. If you weaken your immune system, you become susceptible to infection, if your immune system is too strong it will attack your own healthy tissues. So if you see anything that claims to ‘boost your immune system’ I would steer clear, unless it is the better product for other more tangible reasons.
Skeptoid’s Brian Dunning has a great breakdown of this issue with some great references that you can find here.