1 of 5
Runny nose, sneezing

What the drug does:
Blocks the effects of histamine, a chemical produced when you have a cold or allergies, which causes mucus secretion, sneezing and itchiness.

Active ingredients:
For help sleeping, select medicines that contain antihistamines such as brompheniramine or diphenhydramine. To stay alert, try an antihistamine-decongestant combination. The stimulating side effects of the decongestant may cancel out the drowsiness from the antihistamine.

Who should avoid:
If you need to drive or operate dangerous machinery, stay away from antihistamines and never mix them with alcohol or tranquilizers. Pregnant or nursing women should consult their physician before taking them.