My 10 1/2 month old baby was just diagnosed with a slow onset milk allergy, what to do?

Avoidance: Not sure what "slow onset milk allergy" means. One is either allergic to milk or not. If one has ige mediated allergy to milk - suspected by history and confirmed by skin test and / or blood test - then strict avoidance is the treatment. www.foodallergy.org is a good resource for milk free recipes. Depending on the type of milk allergy one need to also consider whether having an epi pen is needed.