Take patients pulse before first test, and set timer for 10 minutes after drops under tongue. When timer goes off, measure pulse again. If it jumps more than 5 points, you've found one food problem. It may or may not be the one that is causing the major problem, but you are gaining knowledge at this point. When it jumps quite a bit over resting pulse, wait until it comes down a bit at least before testing another food.
Patience is a virtue here.
It may take an hour or so between tests, but the best part of using sublingual is that the amount is small, and the body recovers fast - virtually no chance for anaphylactic shock. You can translate any page on this website into any one of several languages by using the translate button at the bottom of each page. The translation will be literal, and will have some mistakes, but it should be readable for those who do not speak English.