There are 11 allergens associated with hazelnut allergy. Three are airway allergens and the other eight are all food allergens.
Cor a 8 is a lipid transfer protein (LTP). This group of proteins commonly cause allergic symptoms.
Cor a 9 is an 11S protein (also known as legumin like). Cor a 11 is a 7S protein (also known as vicilin like) and Cor a 14 is a 2S protein. These groups of proteins are involved in seed storage and are common in many nuts and seeds. This is why a person suffering from a tree nut allergy is often allergic to most nuts and seeds.
I have put together some more comprehensive resources at http://www.allergyresources.co.uk/Hazelnut.php
The allergy resources page for hazelnut covers the key allergens, which allergic syndromes are linked to this allergy and other foods which are commonly cross reactive with hazelnut.
There is also regularly updated links to useful websites specifically for hazelnut allergies and the latest research papers on the topic.
If you have multiple allergies and are interested in how they are linked or want to find out more about food allergies outside the usual top 14 then you can follow me on Facebook or Twitter, where I share a food allergy card every day of the week.