[header] How to treat an infected blister [title] Consider if you should drain the blister. [step] Usually, you should leave an unpopped blister alone to prevent aggravating it and making the infection worse. But, if your blister is on a joint and places pressure on it, you may want to drain it. 
[substeps] Draining the pus can relieve the pressure and reduce pain. Keep in mind that you'll need to monitor the blister and keep it bandaged and clean after you drain it.