Allergies are the result of a hypersensitive immune system. The allergic immune system misidentifies an otherwise innocuous substance as harmful, and then attacks the substance with a ferocity far greater than required.
Laying off an employee is different from firing an employee. Firing means letting a worker go for any reason, whereas a layoff refers to an employment termination based on economics, usually involving more than one worker.
What's insane is that Sandberg felt the need to hide the fact, since there's a century of research establishing the undeniable fact that working more than 40 hours per week actually decreases productivity. In the early 1900s, Ford Motor ran dozens of tests to discover the optimum work hours for worker productivity.