I cannot answer your question, but there is an extremely effective product for cold sores that costs very little to make yourself and should do the job.

This is Colloidal Silver and there is a forum here for it. I make my own using a Sota Instruments Silver Pulser.

A relation was visiting a couple of years ago who got cold sores regularly. She had one coming up and expected it to burst through by morning. I suggested she try a silver water spray on her lip which she did. We could not see it yet, but she knew it was coming. It did not eventuate and she sprayed it every two hours the first night from about 5pm to 11pm, then again in the morning and when she thought about it in the day. Two days later there was no sign of it and she has used it ever since to do the same thing.