I plan on making a baby blanket for my sister who is due in March, however I am having trouble picking out a yarn that is appropriate for a baby blanket and will be comfortable for the baby.
I only want to use natural fibers… what would be the best to use? I was thinking Debbie Bliss cashmerino… I just want to make sure what I use will not irritate the baby’s skin. Please let me know your suggestions!
New moms aren’t going to have the time to hand wash a cashmere blanket and it will get spit up on every time it’s used. Most baby yarns are machine washable and even though they’re acrylic are very very soft and won’t irritate the skin. Blankets aren’t going to be next to the skin much anyway.
I second the acrylic - babies are MESSY little things and hand washing a cashmere blanket with chunks of stuff in it does not sound fun.
I have used Caron Simply soft and find that if I run it through the washing machine with a gentle soap and fabric softner it feels great.
If you really want to do something out of cashmerino you could make the new mother a nursing shawl - that would seem less likely to get dirty.
I would do either cotton or a washable wool. I’m going to pick one of these for myself. The baby will be born in Spring so most likely cotton. Knitpicks is my favorite. Or you could do an organic cotton. 
What about hemp? Look into some of the other, less common fibers too, like a linen maybe. I would think all of those would work. Plus they are natural and washable.
Bernat cotton tots is great! I’ve knit blankets for all my friends spring/summer babies in it. My godson is almost four now and still has the blankie I knit him, it has just gotten softer and more cuddly as the time has gone by. My best friend, his mom, loves it because she can just throw it in the washer and dryer when it gets dirty. This kid is like Linus from The Peanuts cartoon so it get dirty!
I’m also making a baby blanket ofr my cousin. I’m using Plymouth Encore for it.