  The issue of the observability of the Lamb shift in systems with
non-degenerate energy levels is put to question. To this end, we compute the
Lamb shift of such systems in the electromagnetic environment provided by two
infinite parallel conducting plates, which is instrumental in demonstrating the
existence of the so-called Casimir effect. A formula giving the relative change
in the Lamb shift (as compared to the standard one in vacuum) is explicitly
obtained for spherical semiconductor Quantum Dots (QD). It is the result of a
careful mathematical treatment of divergences in the calculations involving
distribution theory, which also settles a controversy on two different
expressions in the existing literature. It suggests a possibility of QD
non-degenerate energy spectrum fine-tuning for experimental purposes as well as
a Gedankenexperiment to observe the Lamb shift in spherical semiconductor
quantum dots.
