US research published in the Lancet medical journal found the patch was 75% effective against diarrhea attacks caused by E. coli among volunteers.
The patch contains the poisons produced by E.coli, with the idea that this primes the immune system to cope better when confronted with the real thing.
Patch-wearers who did fall ill recovered far more quickly, it said.
Stomach upsets are commonplace among people travelling to certain parts of the world, and the symptoms - vomiting, diarrhea and stomach cramps, can often leave people incapacitated or weak for days.
A UK travel medicine specialist stressed only 40% of diarrhea cases were caused by E. coli.
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