Suggest Treatment For Itchiness In And Around Vagina?

we have just been back from lakshadweep, & 2 days prior to our return i developed this rash in & around my vagina. its burns & causes major itchiness in & around my vagina & anus. even the labia skin has swollen & wrinkled up. no matter wat i apply, there's no relief. not to forget to mention that the running tap water that came in lakshadweep even that was salty. please help