Summary Background:Alongside hazel, alder and birch pollen allergies, ash pollen allergy is a relevant cause of hay fever during spring in the European region. For some considerable time, ash pollen allergy was not routine-ly investigated and its clinical relevance may well have been underestimated, particularly since ash and birch tree pollination times are largely the same. Ash pol-len extracts are not yet well standardized and dia-gnosis is therefore sometimes unreliable. Olive pol-len, on the other hand, is strongly cross- reactive with ash pollen and is apparently better standardized.  erefore, the main allergen of olive pollen, Ole e 1, has been postulated as a reliable alter native for the detection of ash pollen sensitization.Methods:To determine to what extent speci c IgE against Ole e 1 in patients with ash pollen allergy is relevant, we included 183 subjects with ash pollen al-lergy displaying typical symptoms in March/April and positive skin prick test speci c IgE against Ole e 1 (t224) and ash pollen (t25) and various birch allergens (Bet v 1, Bet v 2/v 4) in a retrospective study.Results:A signi cant correlation was seen between speci c IgE against Ole e 1 and ash pollen, but also to a slightly lesser extent between IgE against Ole e 1
and skin prick test with ash pollen, the latter being even higher than IgE and skin prick test both with ash pollen. No relevant correlation was found with
birch pollen allergens, demonstrating the very lim-ited cross-reactivity between ash and birch pollen. Conclusion:It appears appropriate to determine speci c IgE against Ole e 1 instead of IgE against ash pollen to detect persons with ash pollen allergy. Our  ndings may also support the idea of using possibly better standardized or more widely available olive pollen extracts instead of ash pollen extract for all-ergen-speci c immunotherapy.