Why is high humidity bad?

[Cosworth]

It's been hot and raining the last couple days (more than it has since I first got my beardie), and his viv's humidity is shooting way up.

Why is high humidity bad, and what duration of high humidity is bad? A couple days of humidity, multiple weeks of high humidity?

 

[renich]

High humidity can cause respiratory infections. I'm not sure how long a bearded dragon can endure before problems occur.