 [ Symptoms ] 4 yr old son has a rash that comes and goes no other symptoms dr do not know what it is need help please no new detergents or foods nothing has changed in the environment he lives in sometimes it itches sometimes it does not er drs say its a viral thing because they do not know [ Disease ] rash can be caused by a food allergy even though your son is diet has not changed does not mean he can not develop a food allergy or maybe he is now eating more of something he ate little of before so to be sure write down what he ate prior to his rash if you think there is a link between something he ate and the rash let his doctor know here are common food allergies good luck