Allergy testing - does this seem very thorough?

[longerdays]

My daughter (age 8) has been referred to an allergy clinic because she had a bad reaction to (we think) to cashew nuts which necessitated a trip to A&E (very scary). We have had to wait 6 months for a referral and I'm now querying what they actually do. Apparently we need to come for 3 visits in a week a day apart. A plaster is put on her back and this is checked on day 3 (wed) and 5 (fri) to see if it has caused a reaction? To a non professional this does not seem a very thorough form of testing - how many different things can they test off one plaster? Would n't a more thorough test be some kind of blood test where blood can be tested against a whole variety of things which I know other children/adults have had? I am just concerned that this is a rather basic test and we will be left with a very overall picture but nothing specific. Does anyone have some knowledge of this? Thanks.

I've had this form of allergy testing in the past.

I've not heard of this type before.
I have heard of skin prick testing (maybe their method is similar??)
And bloods (rast testing I think it's called)
Neither method is overly accurate unfortunately. My 2 had skin pricks done a while ago, the idea is to put a drop of allergen on arm, tiny scratch on arm within the drop. Wait 15 minutes and measure the size of the lump that may appear.

The test you describe is called a 'patch test' and is more commonly carried out when testing for allergies to non food items. My sister had this done to confirm her allergies to parabens, formaldehyde, nickel etc.
For food allergy testing the most commonly used test is the skin prick or RAST blood test.
Have you queried whether she has been submitted for the right type of tests? My 18yr old daughter has numerous food allergies and has never had the test you describe but has had numerous blood and skin prick tests. Has she been referred to an allergy clinic or dermatologist?