wool alternatives

[daeseage]

I decided ages ago that I was going to make my girlfriend a pair of mittens for her birthday, and recently settled on a pattern and some lovely wool yarn in red and cream. Unfortunately, I just learned that she is very allergic to wool, and I really don't want to give her a gift that will make her break out in hives! So now I need something fairly inexpensive, warm, ideally water resistant, and nice and soft, but I don't know if she will have a reaction to other common animal fibers. I thought about baby acrylics, but I don't know that they'd stand up to the abuse that a comfy pair of wool mittens undergoes, and I don't really care for working with them.

Is anyone allergic/knit for someone who is allergic and have recommendations for wool alternatives?

ETA: Thank you so much everyone for the ideas! She was willing to test out swatches (for science!) from scrap yarn as I had time to knit them, and it looks like alpaca will work for her. Those of you who thought it was the length of the fibers might be right, since the swatch of the wool I'd originally purchased resulted in hives. =[

For those of you that asked about acrylics, part of the reason is that I've had issues with using them in colorwork patterns, and also because there's a good chance that she'll be wearing these while around a stove or open flame. A singed mitten is a lot easier to repair and less hazardous than a melted one!