  Axion-like particles (ALPs) are hypothetical entities often invoked to solve
various problems in particle physics to cosmology. They are one of the most
promising candidates to explain the elusive dark matter. A way to search for
ALPs is through their effects on photons. In the presence of external magnetic
fields, ALPs and photons can convert into one another, leading to measurable
signals. In this contribution we present results of Monte Carlo simulations of
ALP-photon interconversion in magnetised environments. We focus on high-energy
gamma rays with TeV energies travelling over cosmological distances. We include
a full treatment of the intergalactic electromagnetic cascades triggered by the
gamma rays. Finally, we discuss the impact of this improved treatment of the
propagation for current and future ALP searches.
