Alpaca is not wool. Wool, by definition comes from sheep. Alpaca comes from -- alpacas. Many people who are allergic to wool have no problem with alpaca. It's lovely, soft and very warm.
Camel's hair, llama and cashmere yarn also come from animals other than sheep, and they are less allergenic than wool.
BUT: a lot of wool "allergies" are really just sensitivities to any scratchy, rough fiber. or to lanolin. You don't know if you have a true allergy unless you've been tested. Merino wool, which comes from a special breed of sheep, is very soft, and many people who think they can't wear any wool have no problem with it.
You can also wear a layer of another fiber next to your skin to neutralize any possible allergic reaction -- a camisole, a t-shirt, a scarf at the neck, etc.