As soon as my kids start having symptoms of a cold I start to use this cold syrup. I notice a difference within a day of using this. At night if they cough a lot 4 out of 5 times within 30 minutes of giving this to them my kids have fallen asleep and almost completely stopped coughing for the night. I always make sure to have this on hand, especially during cold/flu season. Hylands makes great products and this is one of them.