Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain it seems that you are suffering from allergic reaction as the symptoms itching over the body and head and on consuming chillies is indicating towards allergic reaction.. It can be due to causes like allergy to any food or medicine, contact dermatitis caused with any skin cosmetic, soap, detergents etc.. While certain grasses, trees etc can also cause allergy.. I would suggest you to consult an Allergist and get allergic tests like Patch test, RAST test, food challenge test etc can help in diagnosis and treatment can be done accordingly.. The tests will help in ruling out the exact cause of the allergen and once you know the cause of the allergic reaction you can avid exposure to it to prevent allergy attack.. He can be advised to take anti allergics like benadryl along with steroid ointments..alamine lotion can help.. Applying C Do cool compresses or take cold water bath.... You can also be instilled an Immunotherapy that will help in reducing the severity and frequency of allergic attack.. Once the allergen is ruled out avoiding exposure to it can prevent the allergy symptoms.. Hope this information helps.. Regards..