Research has shown that the principal cause of cetuximab-induced anaphylaxis is anti-oligosaccharide IgE antibodies specific for galactose-α-1,3-galactose (α-Gal) present on the mouse-derived Fab portion of the cetuximab heavy chain. Furthermore, it has been revealed that patients who are allergic to cetuximab also develop an allergic reaction to mammalian meat containing the α-Gal owing to cross-reactivity, and the presumed cause of sensitization is tick bites. The prevalence of red meat allergy is high in Shimane Prefecture located at the western mountainous area of Japan, as is tick-transmitted Japanese spotted fever. On the other hand, Tokyo Medical and Dental University (TMDU) is located in an urban area, so there are few mountains and forests and the occasion of tick bites are limited. In this study, we aimed to clarify the difference of α-Gal and/or cetuximab specific IgE retention rate in Japan. 
We enrolled 100 subjects from Shimane University and 50 subjects from TMDU, who had consulted with complaining anything except food allergy. We interviewed about their clinical background. Serum specific IgE antibodies to α-Gal and beef were measured using  ImmunoCAPTM. Furthermore, serum specific IgE antibodies to cetuximab was measured using immunoblotting.
As a result, the α-Gal-specific IgE were detected (≥ 0.10 kUa/L) in 16 out of 100 subjects in Shimane University and 8 of 50 subjects in TMDU. Moreover, among them, 11 of the 16 in Shimane University and all 8 in TMDU were positive (≥ 0.35 kUa/L) for the beef-specific-IgE test. Additionally, immunoblotting showed 5 of 100 subjects (5%) in Shimane University and 2 subjects (4%) in TMDU have IgE antibody to cetuximab.
This study showed that there is almost no difference of α-Gal and/or cetuximab specific IgE retention rate between rural area and urban area in Japan. Therefore, clinicians should be aware of allergies caused by α-Gal all over Japan.

Prevalence and regional differences of sensitization to galactose-α-1,3-galactose and/or cetuximab in Japan