Normally I rotate between a couple of different brushes and soaps/creams. For the past few months I've primarily used either a synthetic (Razorock) brush with TOBS Sandalwood cream or a boar brush with various Stirling soaps. Most of my shaves up to this point have been with the boar brush and Stirling soap. Beginning sometime last week I was loading up TOBS with the Razorock synthetic. The lather went on and as I was beginning the first stroke of the razor, I began noticing a very mild, almost what I would describe as a "burning" sensation all around the lathered area. Not enough to be uncomfortable, but definitely noticeable. I completed the shave and chalked it up to something in the TOBS that disagreed with me. Following that shave I decided because "I must be sensitive to the TOBS", I returned to using the Stirling soap with the boar brush. No problems, no discomfort from that mild burning sensation. Thursday morning I decided to continue using my Stirling lather but this time I lathered it up with the Razorock synthetic. The mild burning sensation returned. Now I was really confused. I would have never thought a synthetic brush could have anything to do with something like that. Yet there was that mild burning sensation. There was no post-shave residual redness or other after-effects past the feel of the mild burning while lathering. So this morning I used the exact same soap as Thursday...Stirling sandalwood, only this time I used my Razorock best badger instead. There was no burning sensation or discomfort. Just a normal, comfortable lather. Maybe this is already something known in the community but I was always under the impression synthetic brushes were least likely to create issues with skin compatibility. I've used synthetic brushes many times before and never noticed anything like this, it's only recently this is happening. Two different soaps/creams from two different makers (though I suppose similar ingredients could be in both) leads me to believe the issue is solely with the synthetic brush, but does not happen with two different types of natural hair brushes. Anyone else have this experience?