It's well known that stress weakens the immune system[1]. So it's not a surprise that stress might encourage dormant infections (such as HSV-1) to enjoy a resurgence.

[1] https://www.apa.org/research/action/immune

I get canker sores [0] only during periods of extremely high stress or sleep deprivation.

[0]https://en.wikipedia.org/wiki/Aphthous_stomatitis

Speaking anecdotally, sleep deprivation is the biggest immune system damper for me. Often it’s hard for me to judge the effects of stress per se, because sleep deprivation also leads to stress and vice versa.

If you ever had chicken pox, high stress can re-activate the dormant virus, and it reactivates as "shingles". There is a vaccine that came out a few years ago to suppress it from happening.

I think the vaccine is only covered by insurance (USA) for people over 50 in most cases. If you are lucky enough to have coverage, get the vaccine. Shingles as an otherwise healthy 42 year old was no picnic, I can't imagine how bad it must be for someone older or more immuno-compromised.

AFAICT both the options for shingles vaccination are just variants on the chickenpox vaccine - one being more directly just a high dose of it.

This doesn't undermine anything you say, I'm just bemused at the lag time between the chickenpox vaccine (1984) and Zostavax (2006).

Had chicken pox in my 30s. Not good. The shingles vaccine isn’t expensive, thank heaven. It’s a quarter century later and my mom got shingles at about this age…