It stops you scratching for a while, but does not stop the reaction.
If you know you react badly, the best thing you can do is (a) take a long-acting anti-histamine twice a day every day, starting the morning you leave for your trip, and (b) cover every millimetre of skin with either clothing or DEET.
Heat applied to the bite is supposed to break down the proteins in the bugs saliva that you are reacting to. As a fellow reacter, I'm tempted to buy one of these amzn.eu/d/gkIjJCX, as it's pretty difficult to heat a teaspoon when you're out and about.