Hi Multi strain probiotics are more of a cocktail approach to digestive health. the single strain variety are usually more targeted at specific things. try them one at a time to see if you can find one that works for you. i suffer from sinus, all teh time in teh colder months and sometimes even during the summer on occasion too. i am not familiar with any studies that would indicate a definate link to probiotics having an effect on sinus. BUT that dosent mean that there arnt any that work for it, it just means that they may not have been identified yet. im also not entirely sure on teh action that probiotics would have directly on siusitis. i have done some very very silly things with probiotics over the last decade, but shoving them up my nose isnt something i have tried.! YET............CheersIan