  We demonstrate that in unquenched quantum electrodynamics (QED), chiral
symmetry breaking ceases to exist above a critical number of fermion flavours
$N_f$. This is a necessary and sufficient consequence of the fact that there
exists a critical value of electromagnetic coupling $\alpha$ beyond which
dynamical mass generation gets triggered. We employ a multiplicatively
renormalizable photon propagator involving leading logarithms to all orders in
$\alpha$ to illustrate this. We study the flavour and coupling dependence of
the dynamically generated mass analytically as well as numerically. We also
derive the scaling laws for the dynamical mass as a function of $\alpha$ and
$N_f$. Up to a multiplicative constant, these scaling laws are related through
$(\alpha, \alpha_c) \leftrightarrow (1/N_f, 1/N_f^c)$. Calculation of the mass
anomalous dimension $\gamma_m$ shows that it is always greater than its value
in the quenched case. We also evaluate the $\beta$-function. The criticality
plane is drawn in the $(\alpha,N_f)$ phase space which clearly depicts how
larger $N_f$ is required to restore chiral symmetry for an increasing
interaction strength.
