In light of recent findings which associated C3 upregulation in trigeminal ganglions with itch in a chemical-induced mouse model of allergic contact dermatitis, it is tempting to speculate that the early upregulation of C3AR1 triggers itch sensation in BP (71), in particular as pruritus is present in nearly all BP patients and is not limited to areas with visible skin lesions (9). Here, C3 is linked to allergic contact dermatitis.