Healthy worker effect - what is it?

What is the healthy worker effect?

That is if people that get sick from the workplace exposure stop in the job (maybe already after a few days) and only those that can stand the exposure remain.

This has for example been seen in hairdressers

https://onlinelibrary.wiley.com/doi/10.1111/j.0105-1873.2006.0775f.x

One way hairdressers can lower their chemical exposure to limit the risk of allergic dermatitis (one type of eczema) is to use gloves when in contact with chemicals - for example during hair dying