Am not a doctor but I have used ICES nearly daily for three years. Sometimes for as little as a few minutes and sometimes longer than four hours. Power level as low as five on sensitive areas and all the way on denser areas. I’ve used an A9, M1 and C5.
My various theories I’ve adopted or personally have include that it rapidly accelerates detoxification and removal of free radicals from the body. It’s also in essence a massively anti-inflammatory influence.
I believe the NRF2 pathway in the body is what is most responsible for free radical waste disposal and after about age twenty one that body process goes dormant. Vitamin C gives a boost but is inferior to this body process and a few natural supplements claim to be able to restore that function. Protandim, invented by a Mormon company, claims to be one of them. It’s an MLM but a DO friend was a distributor so we tried it and definitely felt better. In conjunction with ICES (And without it) we did not experience what you have described.
Pulsing water on low power / 4pps for 5 minutes might give you a boost too but it will almost certainly cause a detox for the first 2-3 days. Dr. Pollack might be able to speak to it more.