Why is my female dog aggressive after her male dog returned home?

Sometimes dogs don't like the change in smell when another dog comes back from the vet. You may want to wipe down the older dog with a damp cloth and brush her to get the vet smell off her. It also can be that he now sees she is weak and he wants to take over being the top dog. This can be dangerous as he could fight with her and hurt her so you are right to keep them separate when you are not there to monitor their behavior. If your younger dog is well trained I would make it clear to him that this is inappropriate behavior by your voice and placing him in a crate or outside when he exhibits this behavior. Hopefully in a few days things will settle back into the normal routine. Thanks for using Petco Pet Education Center, formerly Petcoach to help you get answers to your veterinary questions.

WIth some patience and training, they may be able to get along. Consider a pheromone product, such as the Adaptil Collar or DAP plug in diffusers, to decrease any anxiety or aggression in the home. If you have cats, use Feliway Spray or plug in diffusers. You didn't specify the species in the post. Keep them separate, then gradually introduce (or re-introduce) them. First, allow them to hear and smell one another through a closed door. As they progress, you can allow them to see one another but without physical contact. Correct any aggressive or negative behavior immediately. The next step would be to place one of them in a closed carrier and leave them in the same room. Do this for ever increasing periods of time until they are acclimated. Finally, allow short, supervised playtime. Be consistent and praise/reward good behavior. Separate them if they get "rowdy" until they settle down, then reintroduce them.

Separate them for a few days then gradually reintroduce them. First with a door between them so they can hear and smell one another then separated so they can see but not reach one another and finally a supervised physical introduction. Use leash, collars and muzzles if necessary. Pheromone products such as the Adaptil collar or DAP plug in diffuser may decrease any anxiety or aggression. Provide adequate numbers of bowls, beds and toys to prevent food aggression or resource protection.

Gradually increase the amount of time they are physically together as long as there is no aggression. Correct any negative behavior immediately. Consider a pheromone product, such as the Adaptil collar or DAP plug in diffuser, to decrease any anxiety or aggression. Provide additional bowls, toys and blankets to prevent resource protection. If the behavior persists, consider a consultation with a certified veterinary behaviorist.

I'm sorry your pups have been so ill. Being sick with Parvo, being isolated and going through the treatment is very stressful on dogs. They come home from the vet smelling funny and they may still not be feeling perfectly yet. First step is to keep them apart but try to have a baby gate between them so they can see and smell each other but not reach each other. Try to give them both equal attention and love. Reintroduce slowly, maybe in a more neutral space, like the back yard. Try a product like Adaptil, which is a dog pheromone that reduces stress. You can get it in a collar or a spray (the spray you would put on a bandanna then tie around the dog's neck). This can really help to calm. Just try to be relaxed with them and give them time-- most dogs will come around once they settle back in.

Hi there. Actually, yes! To reasons not always know to us-changes in the hormonal makeup of our animals (i.e. a recent neuter) can make them smell different. Many theories have been postulated as to why previously accepting partners will turn away the new "smell" and show aggression. Many think it is frustration in the change. Some think it is because they now want to show dominance. Often, we do not ever really know for sure. Normally with time the pair will acclimate again, but I usually recommend supervised playtime until then. I hope this helps!

It may take some time for her to accept him. If she is being aggressive toward him than you should not allow them to be together unsupervised, espeically around feeding time or any toys/bones that she may protect. Give her extra attention, praise, and treats while the puppy is around so she knows he is not there to replace her. You could also try an Adaptil collar or diffuser and see if that helps. If she doesn't start accepting him than you could talk to your vet about trying an anti-anxiety medication, like Prozac or Trazodone and see if that helps.