Angliści.pl present, czyli Idiom Tygodnia Anglistów.pl:

To get out of hand

Explanation, czyli o idiomie nie-idiomatycznie:

If things get out of hand, it means that someone has lost control over the situation. It is used in a negative context.

Examples, czyli Zdania Do Zapamiętania:

• "Their argument was peaceful and civilized at first, but things quickly got out of hand and soon they were punching each other on the floor."
• "At first just a few students were giving each other answers, but when the teacher stepped out of the room for a moment, the cheating really got out of hand."
• "And then... then I fell asleep... and everything... I mean the mouse... got out of hand... I mean - of paw... I mean out of the cage... And now... now I am hungry" - said the cat sadly.

Where and when to use, czyli kto doceni naszą elokwencję:

The expression is used in both American and British English - universally, except for very formal language.

Our Polish Equivalent, czyli to coś, co nie zawsze jest:

hmm..... coś wymknęło się spod kontroli;

Za idiom dziękujemy

Erikowi Wesnerowi

(Erik, thanks!)