I developed a hot/swollen/bumpy rash on and around the site of my old points.
I have also had this occur once and I thought that was quite interesting. I am also pitta dominant.
Leaving kambo on for a half hour is okay so long as you don't have a weak heart. This is up to to the practitioner, provided they have experience.
It is a way of conserving kambo, and not needing to add more. It does not do much unless the points are misted with water to rehydrate the kambo and the tissue to allow absorption,
as the areas and globes begin to dry out.
A normal effect of kambo is skin flushing and blotched patches of red skin.
I would not be concerned with it, and your first practitioner had insight.
As well as the fact that the lymph system works with the cardiovascular system to circulate and filter waste,
which could lead to you seeing bumps and rashes on the surface of your skin.
You didn't get any pictures did you? I wish I could have seen the condition, esp. the scarring at the old points.
Update and let us know if this eventually clears up.
I'm sure a few methods would help to prevent that from happening again, but I would have to think on this, as far as not going against the functions of the kambo.
Afterwards you could take a shower and turn the water to cold as well as focusing the cold water on the areas with the inflammation to relieve the inflammation.
Cold water will also help flush the circulatory system/organs and bring down inflammation and cytokines which cause inflammation.