Skin allergy type. Needs to be done!

Hi, one of my relative has diabetics and recently they had stopped taking tablets for a week then she was getting some allergy type bubble rashes on skin. Then they consulted diabetologist. They changed tablets and even then she was getting rashes. They consulted again. Doctor said consult skin specialist. They consulted skin specialist.Now skin specialist said rashes are due to food allergy and now we are strictly following food intake. Even then rashes are appearing on skin. Now we are in a confusion state either we shld consult diabetics doctor or skin specialist. Are rashes appearing because of tablets side effect or is it really food allergy. Please suggest me what needs to be done Thank you. Hope she is not having some big problem