During the 12-week study, subjects will take 2 capsules 5 times daily (approximately every 3 hours) for 2 days each time they feel symptoms of an acute respiratory illness (ARI) are starting. Thus each subject will ingest the equivalent of 3.4 grams of dried echinacea root during the first two days of ARI onset. No additional echinacea (or placebo) capsules will be taken after the first two days of illness onset until the next ARI episode is experienced.