Yes, giant foxtail can harm your pets. According to PetMD, foxtail seeds have backward-facing barbs that burrow into the skin, introducing dirt and bacteria. In worst-case scenarios, they can make their way to internal organs. You may be able to remove the barbs with tweezers, but they can be difficult to completely remove.  Get veterinary help if they lodge in your pet’s eyes, ears, nose, or mouth.