  The equations for the QED effective action derived in \cite{fm} are
considered using singular perturbation theory. The effective action is divided
into regular and singular (in coupling constant) parts. It is shown that
expression for the regular part coincides with usual Feynman perturbation
series over coupling constant, while the remainder has essential singularity at
the vanishing coupling constant: $e\rightarrow 0$. This means that in the frame
of quantum field theory it is impossible "to switch off" electromagnetic
interaction in general and pass on to "free electron".
