Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. From your explanation rash on chest and abdomen that is spreading to legs and feet seems to be most probably due to allergic reaction leading to Dermatitis. As it is spreading you should consult an Emergency room and get evaluated. You can be advised anti allergic medicine like Fexofenadine or Levocetrizine and also a steroid shot can be given to reduce the inflammation and rash.. Also doing cool compresses over the skin, applying Caladryl lotion and steroid ointment like Betamethasone can help in Improvement. Also if allergy is only ruled out then an Allergy test can be done for confirmation of the exact cause of the allergy.. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Honey Arora