My allergist used 0.08 ku/l for rast so if an allergen shows over 0.08 ku/l is it an allergy? or is it if it's over 0.35 ku/l that it's an allergy?

>0.35 IU/ml: When interpreting the results of rast, <0.35 iu/ml of ige antibody indicates absent or undetectable allergen-specific ige antibody. 0.35-0.69 iu/ml of ige indicates a low level of allergen-specific ige. Ige is the antibody associated with a type i allergic response. Today, newer, more sensitive fluorescence enzyme-labelled assays exist and are recommended over rast.

Nope: Skin tests, rast tests or serum specific ige alone can not diagnose food allergy. There is a very high false positive rate with rast testing, especially at the lower vaules. These labs must be interpreted in the context of the clinical history and doctor supervised food challenges can be done when there is confusion.