come to a head, bring to a head

1. if a problem or a disagreement comes to a head, it becomes so bad that you have to start dealing with it. 

• Things hadn't been good between them for a while but it all came to a head last week when Phil failed to come home one night.
  

2. to reach a stage in a difficult situation when someone takes a strong action to deal with it. 

• The crisis came to a head when the teachers' union threatened to sue the city.
  

... http://idioms.thefreedictionary.com/come+to+a+head

3. bring to a head: Cause to reach a turning point or crisis. For example, 

• Management's newest policy has brought matters to a head. 

    The related phrase come to a head means "to reach a crisis," as in:

• With the last break-in, the question of security came to a head. 

These phrases allude to the medical sense of head, the tip of an abscess(농양, 종기) that is about to burst. [Mid-1500s] 

... http://www.answers.com/topic/bring-to-a-head