Concepts related to parity-time symmetry, such as anti symmetry, have found broad applications in wave physics. Systems are explained by Hermitian operators, whereas combination of loss and gain introduces their odd properties. We suggest the associated physics need not be limited to wave dynamics, and we consider processes described by diffusive dynamics. We study the heat transfer in 2 media that is countermoving and reveal that anti — parity-time symmetry is exhibited by this system. The spontaneous symmetry breaking causes a phase transition from temperature profiles. Our results extend the notions of symmetry that is parity-time beyond wave physics and may offer opportunities to manipulate mass and heat transportation.