If you’re knitting an item of clothing for a baby or someone with allergies and sensitive skin, it’s best to use yarns with primarily plant-based or synthetic fibers. These fiber types do not contain lanolin or other allergy-inducing chemicals. It’s also best to use a yarn type that is soft, breathable, and gentle on the skin like cotton. Some popular yarns like mohair and polyester can feel scratchy and uncomfortable, even if they’re not allergy-inducing.