
York Testing is just taking bloods and sending them off for analysis.
Its a very effective way of finding out what/if your pet is allergic to anything. They will check for indoor allergies. e.g. house dust/storage mites and outdoor ones, like as you say pollen, grasses, etc and also if there is anything in the food that they might be sensitive too, like wheat/gluten/chicken/beef/eggs etc.
They can be inhaled or in touch contact with or eaten so its abit of a minefield but this test will tell you for sure what the problem may be.
Good luck and I hope they manage to sort your dog for you.