The equivalence between irreversibility and dissipation entails that the Onsager reciprocal relations hold unconditionally, requiring the part of the phenomenological matrix describing dissipative phenomena to be symmetric. The antisymmetric part of the phenomenological matrix corresponds to the Casimir's variant of the reciprocal relations and describes reversible phenomena. Further, we discuss the relationship of the reversibility and entropy production, including the role of the level of description, and we use the chemotaxis as an illustrative example.