If there's one thing that sends new puppy owners into a quiet panic, it's the biting. Those needle sharp teeth, the way a sweet snuggle turns into a shark attack on your sleeve, the bruises on your hands by week two. I hear it constantly: "Is something wrong with my puppy? Is he aggressive?"
Almost always, the answer is no. Puppy biting is one of the most normal, predictable, developmentally driven behaviors there is, and understanding what's actually happening underneath it makes the whole stage far less frustrating to live through.
Puppies explore the world with their mouths
Long before a puppy can use its paws with any precision, the mouth is its primary tool for investigating everything: texture, temperature, whether something is food, whether something is fun. In that sense, mouthing is closer to a human baby putting everything in reach into their mouth than it is to anything aggressive. It's information gathering.
It's also social. In a litter, puppies learn bite inhibition, meaning how to control the force of their jaws, by biting their littermates and mother and getting feedback when they bite too hard. A puppy taken home a little early, or a singleton with no siblings, often misses some of that early schooling, which is part of why some puppies seem mouthier than others. The good news is that bite inhibition can still be developed with the right guidance later on.
Then there's teething, and it happens twice
Here's the part that surprises people: puppies teethe in two waves.
The first wave happens before you even bring your puppy home. Those tiny baby teeth, 28 of them, sometimes called deciduous or "milk" teeth, begin erupting at around three weeks of age, while the puppy is still with the breeder or litter.
The second wave is the one you experience. Starting around three to four months old (roughly twelve to sixteen weeks), those baby teeth begin falling out and the permanent adult teeth push up through the gums to replace them. By the time it's finished, usually around six to seven months, your dog will have a full set of 42 adult teeth. You may find a tiny tooth on the floor, or you may never see one, because puppies often swallow them harmlessly while eating.
This second wave is the sore one. Gums get inflamed and tender, and chewing provides real, physical relief, the same instinct that has a teething human baby gnawing on everything in reach. So when your four month old suddenly seems determined to chew the leg of your coffee table, it usually isn't defiance. It's discomfort looking for an outlet.
Why it sometimes feels worse, not better
A few things stack on top of teething to make biting spike:
- Overtiredness. An overtired puppy is a bitey puppy. Just like a cranky toddler, an under rested puppy loses the ability to self regulate, and the mouthing ramps up, often in that classic early evening "witching hour."
- Overexcitement. High arousal and biting are closely linked. The more wound up a puppy gets during play, the harder it is for them to keep their teeth to themselves.
- Developmental leaps. As puppies move through their growth stages, behaviors you thought were fading can briefly return. It's normal.
None of these mean your puppy is bad. They mean your puppy is a baby with an immature nervous system and a mouth full of erupting teeth.
What helps, and when to call your vet
Giving your puppy appropriate, safe things to chew is the simplest form of relief, and protecting their rest is just as important. The actual skill of teaching a puppy to be gentle with their mouth, true bite inhibition and redirection, is something I work on with clients directly, because it depends a lot on the individual dog, the household, and getting the timing and consistency right.
A couple of things are worth a vet's eyes, though. If a baby tooth doesn't fall out as the adult tooth comes in (a "retained" tooth, more common in small and flat faced breeds), it can crowd the mouth and needs to be checked. Mild gum bleeding during peak teething is normal; heavy or persistent bleeding is not.
The short version
Puppy biting is developmental, not a character flaw. It's mouthing, social learning, and the genuine discomfort of two rounds of teething, all happening in an animal that's still, essentially, a baby. It passes. And with the right foundations laid early, the puppy who's gnawing your hand today becomes the gentle, well mannered adult you're hoping for.