If you don't have a bacterial infection, you don't need antibiotics. If the root of the problem is viral in nature, as is often the case with a cold, antibiotics won't help. Did the doctor specifically say your congestion was due to a bacterial infection? I ask because I worked in the healthcare industry for years and many doctors ALWAYS write a prescription for an antibiotic, without even bothering to check for the presence of bacteria. They've been conditioned to write these prescriptions because the big name pharmaceutical companies offer them kickbacks, but it's not always in your best interest to take them, especially if you don't actually HAVE a bacterial infection.