Although human hair is non-toxic for cats, hair fibers consist of high amounts of sulfur, structural lipids, and keratin proteins that cats can’t absorb.
Hair ingestion over an extended period can cause gastric irritation and vomiting.
Suggestions
If your cats like to eat human hair, monitor their behaviors and try to identify any underlying issues such as anxiety or stress.
If the behavior persists, consider consulting a veterinarian.
Note: even if labeled as safe, any food can potentially cause allergies. When introducing a new food, please feed a small amount and observe your cat for any allergic reactions.