I’ve been lucky enough to have found GPs who have listened and assisted in getting my children’s allergy diagnosed relatively quickly. I’ve heard anecdotes from many others who have not been so lucky and their GPs seem to think it unnecessary to refer for allergy testing.
If you find the GP you have seen is not listening are there others at the practice you could get a second opinion from? I found some more resistant than others to treatment, some just didn’t know about allergies so it helped to research the information myself and go in ready to tell them what I needed, eventually getting to know which doctor was the most sympathetic. 7 years ago when we were first starting out there wasn’t that much information about but these days there is a lot more on the web given that the incidence of allergies is increasing,
If you find that your GP is still refusing to do anything the NICE guidelines is a good place to check that they are doing everything they can do diagnose your child’s allergy. If they are not, print it out, go back waving it at your GP telling them they have to fulfil their duty of care. Pester them as much as you can, they will eventually get the message!