Dogs and kids aren’t always a match made in heaven. Kids are notoriously loud and boisterous and dogs are…well? They’re just like us humans, all complicated and moody and full of their own personalities. Some dogs love playing with kids. Some dogs don’t. Some dogs loved playing with kids at one point and then something changed…now they no longer do. Here are four signs to take seriously when you’re wondering whether or not you should keep vulnerable children away from your dog.

1. Your dog is losing his faculties.

Dogs can be “aggressive” (a totally reductive, non-specific term) by nature, but in many cases they resort to aggressive behaviors as a response to something else going on in their lives. As dogs age, they can lose their mental and physical faculties just like humans; this leaves them feeling helpless, confused, and in some cases, with a “fight or flight” response. If your dog can’t see or hear as well as he used to or if he seems a little less “with it” than he did just a year or two ago, it’s time to start monitoring his behavior for more serious signs he could become a danger to others as nature takes its course.

2. Your dog’s behavior is unpredictable.

No dog’s behavior is ever entirely predictable but most dog owners have a general idea of what their dog will do in a given situation. It’s when your dog’s behavior starts surprising you that you need to be extra vigilant. Maybe he instigated a fight with another dog when he usually loves to be sniffed. Maybe he ripped apart your favorite pair of shoes when he’s usually not a chewer. If your dog is behaving in ways that don’t seem to line up with his personality, talk to your vet about what the changes might mean. The key to having a dog safely around children is mitigating the risk, and risks are borne from unpredictability.

3. Your dog growls often.

Growling is one of the most overt signs of aggression in dogs. Gnashing, baring teeth, and low, guttural growls are obvious expressions of, “Stay back!” from your dog. Growling can occur for a variety of reasons – food related, territorial, boundary-crossing – but it should always be taken seriously. If there’s one reliable predictor of physical aggression in dogs, it’s a deep growling noise. If your dog growls, learn to spot the precursors to the growling behavior, like bared teeth or tensed muscles. Knowing these predictors can help you remove your dog from situations in which he might become aggressive.

4. Your dog has bitten someone.

Dog bites are incredibly common, and they don’t always mean a dog is irredeemably aggressive. They can happen as a response to unique stimuli; for some dogs, a bite is something that happens once and never happens again. That said, a dog who has bitten a human being should never, ever be allowed to play freely with children. Kids are the walking definition of stimuli. They yell, they hit, they play too roughly – a dog with a bite trigger simply might not be able to tell the difference between a child and a real threat. If your dog has intentionally bitten someone in the past, remove him from any situation that could potentially result in a repeat of the incident, no matter how unlikely. It’s always better to be safe than sorry.

Do you worry about your dog around children? Talk to your vet. Take care to articulate exactly which behaviors have you concerned, and ask about how you can tactfully remove your dog from situations that could lead to aggression. “Aggressive” dogs are just dogs. They don’t deserve to be maligned, but they shouldn’t be left to their own devices, either. In the same way your dog has a right to feel threatened, children have a right to safety. It’s always your job as the dog owner to take control of a potentially dangerous situation.