Will old cat scent stress new kittens? How should I clean?

It's probably more of a case of a rambunctious kitten than one trying to establish dominance (a very outdated theory). A few things you can try include giving kitten some extra play time to wear him out, making sure your older cats have places to hide and get away from the kitten (such as high up perches or separate rooms), making sure everyone has their own access to food, water, and litter, and using a pheromone diffuser or collar. Pheromone diffusers help by releasing a calming pheromone and are great for inter-cat stress and issues.

If your older cats have been together for several years, they probably have their "territories" picked out. It is quite possible that they just don't like each other. Having more than one pet is often like being placed with a roommate that you didn't choose - sometimes it is a great fit and sometimes you can't wait to move out! It is hard for me to tell you if getting new kittens will help or hurt the current situation, as it would just depend on how happy your current cats would be with new, and very young roommates. Kittens like to play, a lot, and often need to be taught the rules of the house. There will likely be a lot of fighting at the start until the kittens grow up a little. There is a possibility that kittens will help the other cats mellow out together, but my gut feeling is that this may not happen. If you do decide to get new kittens, remember that you will need a drastic increase in litter boxes (and feeding stations and water bowls). Veterinary behaviorists recommend 1 more litter box than you have cats, so that means 6 boxes! And they all need to be in different areas of the house to give a sense of privacy. You will also need additional quiet space so that everybody can feel safe in their own area.

You can use baby gates or covered X-pens to help make the open space a bit smaller as you gradually introduce the kittens to the area. This can help control where they go and make it easy for them to adjust. Shutting doors, etc can also help control the number of areas they go to at once. Once they are more used to the area, you can then open up more space. I also highly recommend a pheromone diffuser plug-in such as Feliway in the room you'll be introducing them to in order to help with stress.

I'm glad you are doing your homework before bringing new fur babies into the situation. Most shelters will routinely deworm their pets and test for leukemia and FIV. So you definitely want to make sure these treatments/tests are run prior to adopting the new kittens. Its not unusual for new cats and kittens to break with upper respiratory infections within the first 2 weeks of being adopted. Herpes virus is very common in cats (some estimate 80% of cats carry the virus) and it comes out in the stress related to being in a shelter and being rehomed. Now, this is not going to happen to every cat/kitten but its not unusual. Therefore, your best chance to avoid this would be to get a cat/kitten that has been kept in a foster home. It will likely still have herpes but the environment should be less stressful, therefore less risk of the virus becoming active. Keep the new pet separated for 2 weeks. That way if it does have an outbreak, you will at least have it contained. You could also put your cats on 500mg of lysine twice daily to help booster their immune system. Kittens get 250mg twice daily. Please post again if you have any further questions!

When you have that many cats, you are bound to have conflict at some point. They may single him out due to his age or size. Separate him for a week or two, then gradually reintroduce him. First, allow the others to hear and smell him but not see him. Progress to sight but without physical contact. Before a physical introduction, place him in a closed carrier in the room with the other cats. Once they have accepted him, you can try a supervised physical introduction. Provide an adequate number of litter boxes (typically one per cat plus an extra). An adequate number of bowls, beds and toys should also be provided to prevent resource protection. A pheromone product, such as Feliway spray or plug in diffusers, may decrease any anxiety in the home.

I suggest you try some Feliway diffusers in the house. Feliway is "happy cat" pheromones and really helps to de-stress cats in these types of situations. https://www.feliway.com/uk Usually adding new cats/kittens to the mix is not a good idea. It usually just causes more stress. Hope this helps.

As a starting point, make sure that both of your cats have been neutered, as intact male cats will often spray urine due to hormone influences. If both cats have been neutered, the spraying behavior is likely a sign of stress and anxiety, but medical causes of inappropriate urination should be ruled out by a visit to the veterinarian. Separating the newly adopted cat and only allowing the cats to interact under direct supervision may minimize fighting behavior. Also, utilizing calming pheromone products for both cats, such as the Comfort Zone® Multi-Cat Diffuser, may decrease the stress level for both cats. If the aggression continues, consultation with a specialist in [veterinary behavior](http://www.dacvb.org/) to get to the root of the aggression, coupled with prescription anti-anxiety medication may be helpful for both cats.