Will liquid omnicef (cefdinir) cause my five month old to have a black tongue?

Colored tongue: Impossible to answer without complete history. Discoloration of the tongue can be from many causes-often the color of a liquid or food. It is often caused by yeast also. When some one is on antibiotics the oral flora changes - bacteria is less, yeast increase; bacteria can also cause color changes. Some diseases, variants may cause changes. See a specialist in oral disease-trained in oral medicine.

Probably: Antibiotics alter the normal oral bacteria, allowing overgrowth of other organisms. Bring the side effect to the attention of your Pediatrician. I would also recommend evaluation by a Pediatric Dental Specialist, a Pedodontist, as there are other causes of this symptom other than antibiotic intervention.