What is the best otc cough medicine?

Antihistamines: Coughs are caused by mucous running down into your lungs from your nose. If you use an antihistamine (such as benedryl, Claritin (loratadine) or zyrtec) to dry up the post-nasal drip the cough will be better. It's best not to use a cough suppressant especially in children because if the mucous is not coughed up it can lead to pneumonia and cough suppressants can have dangerous side effects.