  We modify action in an external electromagnetic field to include effects of
virtual axion-like particle (ALP) excitations. A measurable addition to
QED-Euler-Heisenberg-Schwinger (EHS) action is obtained and incorporated into
experimental constraints placed on ALP mass and coupling to two photons. The
regime of these constraints in which the ALP vacuum effect surpasses the EHS
effect is characterized. We show that probing of the virtual vacuum effect
offers an alternative method in search for physics related to ALPs.
