Diphenhydramine-phenylephrine is a combination medicine used to treat symptoms of the common cold or seasonal allergies, including sneezing, runny or stuffy nose, and itchy, watery eyes. Diphenhydramine is basically an antihistamine that reduces the effects of natural chemical histamine in the body, whereas Phenylephrine is a decongestant that shrinks blood vessels in the nasal passages. You should ask your doctor, before using this medicine, if it is safe for you to use it if you have kidney or liver disease, diabetes, or glaucoma. And if you are pregnant or plan a pregnancy, it is still not known whether diphenhydramine and phenylephrine will harm an unborn baby. Therefore, you must not use this medicine without your doctor's advice. Additionally, it is also not known whether this combination medicine passes into breast milk or if it could affect a nursing baby. So, it would be safer for your baby if you stayed away from it. Bear in mind that the side effects of Diphenhydramine-phenylephrine medicine can include severe dizziness, little or no urination, blurred vision and restlessness.