Accidental delivery of PPD

I'm a nursing student and just wondering if anybody can help me.
What will be the complication or adverse reaction if a Purified Protein Derivative (PPD), for Montaux test, is accidentally delivered vascularly? I've researched this on several websites, but they say is to be carefull not to administer it on the blood vessel. They did not even explain what will happen or a reaction.
Thank you!