hi, your body has developed antibody against these food particles specially against its polysaccharides and proteins parts , wheneve you consume these items , cascade of antigen antibody reaction get started known as hypesensitivity reaction type 1 mediated by IgE type of antibody, causing degranulation of mast cells and release of histamine and other inflammatory cytokines resulting into several allergic reactions including rashes, hives etc. this is an example of failure immunological tolerance occuring due to breach in the mucosa of gastrointestinal tract resulting into entry of these undigested polysaccarides and priteins directly into circulation which are then treated ag foreign antigen by body defence system and these are proccessed and antiboy formation against them is started. you should avoid these food strictly and you can consult an immunologist for its management and for desensitisation if possible. thanks .