well, its a mater of how much. one may need to make a saturated solution and use drops instead. i dont think the purity is a huge deal, though getting the cosmetic grade from mountain rose herb makes sense if youre gonna do it that way.

i go through boron capsules pretty fast.

Ok, it is easyer when you use your avatar, so we can see some posting history.
I dont know the reason for the reaction you had, but the mule team may not be the best choice. Some claim there are additives in it. Anyway not much chance of you taking it again :) if you do go low and slow, cosmetical grade or capsules.

Give it time, though.
Also consider other reasons for it happening, like this made me believe the wild yam was bad for me;

//www.curezone.org/forums/am.asp?i=1382279#i

But then I retested the capsules a year ago; with no reactions whatsoever.

As Iodine may highlight a problem, not causing it, rather bringing onto the surface, similar things may happen with other supplements.
To comfort you just know that the males working in the borax mines, ingest approx 30 mg of boron via the borax dust, daily; without harm to their reproducive system. There was a survey on it some years ago.

I am glad to read about the coffee. I have been putting the borax (pre-liquefied) in my husband's coffee plus the Iodine and potassium and selenium. I should add plus Concentrace mineral drops since I use distilled water.
He is ok with it as long he can't taste it so I put an extra half a packet of stevia in it. Believe it or not it still has a coffee taste :)