This should be a no brainer but is something I forgot during my first few sessions. I am no so sensitive to these types of things but other people may be. So I just wanted to highlight the importance of making sure your skin, as well as the knife/stick you use to administer the venom are clean.
Some isopropyl alcohol will do the trick. Sterilize the skin, and the knife before burning and applying venom to the gates.
Happy Purging!