Your bosses will be wary of them and thus of trying anything on with you. You are entitled to representation at such meetings as they have a bearing on your employment rights which a union will seek to defend. Most likely result will be that you will be subject to ongoing monitoring of your attendance. Future absences could raise the spectre of dismissal but a medical/ disability defence will make that much much less likely. You cannot control the gluten content of every crumb that you ever eat and face possibilities at all times of being accidentally glutened and made ill enough not to be able to attend work. What you could do or request your union official to do is to request that the absences be discounted from the absence procedure tally on grounds of disability. They won't want to open that door but it'll scare the hell out of them enough to make them reluctant to tangle with you, unless of course they are ignorant of employment law and very stupid. All the best. Keep us posted on how you get on.