Since the soles of the shoes are made of natural rubber material, there may be some smell from lack of ventilation during storage in the factory and warehouse. This is normal and does not affect your baby's health. You just need to ventilate them in a cool place for 3 to 7 days (do not expose to the sun) to get rid of the smell.
A gentle wipe down is also recommended before first use to clean out dust from storage. Besides, your child's feet will perspire during usage, try to air the shoes once a week to clear out any odour.