hello..thanks for writing in.
The blotches may be Urticaria
.This is a common condition.Most cases are idiopathic.
Since you have seen it only for a day, you can take anti histaminic tablets like Allegra
to make them subside.If you see them recurring for the best few days , you should visits a dermatologist
to get a course of medications for the same started.
The systemic symptoms may be due to the change in diet/lifestyle in the past few days of your vacation.You can treat them symptomatically now by having rest, anti emetics and proper diet.
Hope this is helpful.Take care!