Lemon juice is more acidic than orange juice and more popular than lime juice. The acid helps to cut through the phlegm in the throat and make it easier to clear out. Honey, taken straight, is as effective at stopping coughs as any OTC cough syrup. It coats the back of the throat and soothes the irritated nerve endings. Unfortunately, the effect only lasts about 20 minutes. So, if you have an acute attack of coughing, it's great. If you've got a constant cough caused by a viral infection, you need something longer lasting.