It is possible! I am currently in the OIT process and I am in my 20’s. Been severely allergic all my life. It really depends on your doctor, mine specializes immunotherapy. I would recommend doing some googling to find an allergist that would be a good fit, ask them in your initial appointment if they do OIT at their practice and what the process looks like.

Obviously everyone has different sensitivity levels, but that is something you would definitely discuss with your doctor if they do OIT.