Yes Simla, you are correct. A good friend of mine recently had a very sore throat/laryngitis which her GP said was most likely viral; it resolved after a week or so. It could have been purely coincidental that FP might have contracted a similar virus at the time of using Throatguard - who knows...My experience with Throatguard is that it does not prevent colds, but I get over them quickly as I no longer get the complications of earache and sinusitis which used to drag on for weeks and make life miserable for me.
I take the point that some people may not take it regularly; I would expect M18 would be a different proposition as tooth decay is painful and expensive and if M18 is truly effective then it makes economic sense to make it part of one's daily dental hygiene routine.