Thanks for your query.Your brother is known to have grade four cancer and on chemotherapy
now.He had chemotherapy one week back which was followed by vomiting
.It is a known side effect of most of the chemotherapeutic drugs to have anorexia
and vomiting So what you think as food poisoning
may be a reaction of these agents rather than a food poisoning So please consult the concerned consultant for proper reasoning and treatment.This can be tackled with I/V fluids, multivitamins and antacids.