What might've caused/been related to POIS when it appeared for you?

[Journey]

What was different in life, might've caused/been related to POIS at time it appeared for you? Do you remember it appearing after anything specific, e.g. virus, stress, illness, surgery, infection, probiotics/antibiotics, bad food, being stung, anything that might be related and was different than usually at time you got POIS.

It'd be helpful as it can help understanding what might've changed in body causing POIS and to see if there are any similarities in origin, etc.

Anything you remember, even if unsure if related, even if small detail, tell it please.