http://www.fda.gov/medwatch/safety/2009/safety09.htm#Anesthetics
and
http://www.fda.gov/cder/drug/advisory/topical_anesthetics2009.htm
In short, topical anesthetics work by stabilizing nerve membranes to block nerve transmission…pain nerves in the case of laser pain relief.
The medications involved are toxic and if applied to large areas can and will pass into the blood stream if applied over a large area of the skin, particularly if occluded and focused by occlusive Saran-type wrap.
As the reports attest, the dangerous effects may be rare but are potentially deadly.
Covering the entire leg area was apparently the cause of the deaths.
So, caution is advised.
The articles in the links are fine but offer no precise advise since precise danger is poorly understood.
What is also not stated is that in at least one case of death, the bikini area was also covered in a thick layer of topical and occluded, for at least 2 hours of time. Since this skin absorbes more drug and does it more quickly anyway, this was a large factor in the toxicity of the situation.