The only time you should worry, and consult your doctor, is if your child has a serious ear infection as well as a cold. This can lead to serious ear damage when flying, and may require antibiotics for treatment before your child is okay to fly.
If your doctor has given your child the okay to fly, there are a few things to make travelling with a child who’s not feeling well a little easier:
Get your doctor to prescribe a suitable baby antihistamine or decongestant. Use it an hour before you’re due to fly.
Saline nose drops are also safe for use on babies and toddlers. Simply use squeeze the drops into each nostril with your child’s head tilted back, and then use the suction bulb. This can be done just before flying, and every two hours during the trip.
If your child is very congested, let him or her drink a bottle or from a sippy cup during takeoff and landing. The sucking motion will decrease pressure in the ear.