Hi,
An allergic reaction to Burn Free would itch, like a giant hive might, with edema.

The blisters came about because the med you put on it closed and sealed the pores. Nature (the brain) sends the fluid to the sight of the burn as a protective fluid in the form of blisters, like a bad sunburn would do the same.

Don't break them. Your skin underneath is probably very tender and raw. Put a anti-b cream over it easy, and cover it.

Then see the doctor or go to the ER. It may not hurt until the blisters break. You have to be careful so as not to get it infected. Boiling water is extremely hot.

Let us know how you make out. Good luck.