Abstract
Ustekinumab inhibits interleukins 12 and 23 and modulates the T helper cell-mediated immune response of Crohn's disease. However, ustekinumab may also exacerbate atopic disease by increasing the T helper 2 cell-mediated pathway. We present the first known case of exacerbation of atopic dermatitis in a patient with Crohn's disease receiving ustekinumab. Additional associations in dose frequency, peripheral eosinophilia, and elevated serum IgE were observed. However, while novel in Crohn's disease, exacerbation of atopy after ustekinumab infusion has been observed in patients with psoriasis and psoriatic arthritis.