Unfortunately, as tempted as you might be to give your baby a cough and cold medicine to try and help her feel better, no over-the-counter cold medicines are FDA approved for younger infants or have been proven to actually improve cold symptoms. Even the ones with images of infants and babies on their packages aren't really approved for young children.
In fact, in discussing cough and cold medicines, the FDA reports that "questions have been raised about the safety of these products and whether the benefits justify any potential risks from the use of these products in children, especially in children under 2 years of age."
Most reports of problems with these medicines come from parents giving too much or giving the medicine too often. So it is not necessarily that anything is the medicines are dangerous when they are used correctly. It is a problem that no one really knows the correct dosage of these medicines are for younger children, which is a good reason why they should be avoided.
Another mistake parents make is giving two medicines with the same ingredients, which can also lead to overdoses, even if each medicine is given at the right dosage. For example, if you give your child Infants' Tylenol and Triaminic Cough & Sore Throat at the same time, then you would be doubling up on the dose of acetaminophen (Tylenol), since they are present in each medicine.
To be safe, talk to your pediatrician before giving any over-the-counter medicines to your younger infant, especially if they are under four to six months old.
Sources:
FDA Public Health Advisory. Nonprescription Cough and Cold Medicine Use in Children. August 15, 2007.
