Had to do a double take at your title, as my DH found out about my botox treatment last night!
His reaction : he said it's very subtle, and he feels lucky to be married to someone who cares how she looks.
The reason that I didn't tell him, was because I'd had it from before we met, and in the early stages of our relationship, we had been in a group of friends, and one person said they might get botox, and he said something like "yuk", so I felt unable to broach the subject with him. The longer it went on, the harder it was to bring up. Fast forward about 8 years, and I stopped getting it done, deciding to see if I could just get away with regular facials, but after about 1.5 years, it became evident that botox really is the only way to turn back the clock! So, I went along unbeknown to him, and had it done. If course, after having none for 1.5 years, he noticed after about ten days, that I was line free, and did a bit of fishing, and I told him the truth. I also told him, that one of the reasons I didn't tell him, is because whether he noticed or not, would be a good marker of how effective it is!
I suspect that your DH is more concerned that you revealed this in front of people, and he must have felt on the back foot.
Yes, it's a poison, but so is alcohol & fags.... and most things are harmful in excess.