IL5 and allergic disease: We observed a positive correlation between IL-5 and vitamin B12 status, which agrees with a previous finding where vitamin B12 deficiency caused a cytokine shift toward a Th2 response.35 Although this is an oversimplification of a complex issue, the Th1 dominance is generally more aggressive, and caused by overstimulation of immune cells (i.e., natural killer cells or T cells), whereas the Th2 dominance can be seen in allergy or low-level systemic inflammation.