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.
When productivity per new employee begins to decline, that is a cue to stop hiring. If your factory is over capacity, you can either cut positions or employees to simplify the process. By streamlining tasks into more easily digestible, smaller tasks, employees become more productive as their muscle memory increases.