Hi,
Thank you posting your question,
From your description you are suffering from acute febrile gastroenteritis/enterocolitis which could be caused by intoxication due to food, chemicals, microorganisms such as viruses (
rotavirus), bacteria (E. coli, Salmonellosis, Shigella, cholera etc), Protozoa ( amoeba= E. hystolitica) etc or reaction or symptom of another underlying diseases condition like immune diseases, infections of other organs etc. You will need to consult with your gastroenterologist or doctor to determine the actual cause of the
diarrhea. You will need to be administered
antipyretic, antidiarrhea and antibiotics medications in order to control the
stomach flu after sampling of your stool for analysis. But first line management of your diarrhea is prevention of
dehydration, so you will need to start immediately by taking oral rehydration salt/solution which could be obtained over the counter and take about 2 to 3 liters daily.
About teh itchy red rashes on your trunk ( front and back), i guess it is
contact dermatitis ( guessing because I have not seen the lesion by myself). This could not necessarily be related to your stomach flu and if related, then your doctor needs to investigate further on an underlying diseases condition that could be the cause of the diarrhea and the contact dermatitis. Performing laboratory test such as
complete blood count, HIV serology, ESR, CRP, stool exams, fasting blood sugar etc could help determine the most probable cause of your illness.
Hope this helps