There is a stray cat hanging around outside my house and upsetting my cats, is there anything I can use to help them be less stressed?
To help your cats be less anxious and concerned about the stray cat I would suggest using a Feliway Diffuser or Feliway Spray, which contains facial pheromones that will give your cats a feeling of calm and security.
You should also try to deter the stray cat from the yard. You could try using a repellents and deterrents in the yard to keep the stray cat away. a range of repellents and deterrents can be viewed here.