Belly buttons can be red and sore when they have an infection, which can happen from a bad piercing or from an umbilical cord problem at birth, says Seattle Children's Hospital and ABC News. Another possibility might include a rug burn or another infection that spreads to the belly button.
The best option for treating belly button infections is to visit a doctor to learn what the problem is so treatment can be prescribed. If the piercing is new, the belly button may be having an allergic reaction, states ABC News. Infants with umbilical cord problems and red sore navels should see a doctor as well. WebMD lists penicillin strain injections and penicillin g potassium injections as the most common treatment for umbilical cord problems.