[DANmode]

It can go the other direction, too: exposure to moldy home environments gave me (now resolved) food sensitivities, dust allergies, pet-associated allergies, etc.

You can definitely undertrain, or overwhelm, the immune system if not cautious!

[Tangurena2]

Don't underestimate the amount of cockroach debris present in a modern home. There's a positive correlation between asthma and in-home roach population.

[kakacik]

Maybe some plywood cheap old US homes full of holes or crevices, but here in Europe if you have cockroach infection and not blind or similarly disabled, you know it. They are not exactly hiding in the evening/night.