There's no age limit to being tested for allergies and a baby can be tested for allergies as soon as they are born.
But until the baby is around 6 months of age the allergy tests that are done are not as accurate as they would be until the baby is at least 6 months of age.
6 months of age is when most babies get allergy tested unless they have some bad reaction to something when they are younger.
A skin test is usually done in babies, children, teens and adults and even a blood test can be done to test for possible allergens that the person or baby is allergic too.
It's recommended to get an allergy test done to see if the baby is allergic to something to prevent health issues.
Some doctors may not want to do a skin allergy test on the baby until around 1 year of age but they will do an allergy test if you notice the baby is allergic to something.
Testing for allergies can be done in babies at any age so you don't really have to wait.