Although it is not highly recommended that you feed your baby mayonnaise of any kind, you will be able to start doing so when they get close to being 12 months of age. The reason why it is not advisable to feed small children mayonnaise is because when they ingest it their stomachs produce a significant amount of acid.
Just make sure that your child does not have any problems with egg allergies as this is one of the ingredients in mayonnaise. As long as they have no food allergies that would keep them from eating mayonnaise it should be okay to feed it to them without risking any serious adverse reactions.