Cayenne Pepper

• Cayenne pepper can protect your flowers from dog damage.Hemera Technologies/Photos.com/Getty Images
  
  Cayenne pepper is one of the most common and effective natural dog repellents. Pet-Net states that the capsicum found in cayenne irritates dogs' skin, eyes, throat and paws, and they will avoid treated areas. You can sprinkle cayenne pepper directly into your garden or around the perimeter of the lawn as a deterrent. In the house, apply cayenne sprays to carpets or furniture. Only a small amount is necessary, as the sensitive canine nose will easily detect the strong smell.
  
  

Vinegar

• The smell of vinegar will get Fido off the couch.Ryan McVay/Photodisc/Getty Images
  
  According to Dogs World 101, cotton balls soaked in vinegar will discourage dogs from coming near. You can also mix vinegar with water, and use as a spray on furniture or carpets to discourage Rover from making himself at home. You will need to reapply at least three times per week for best effectiveness. If your pet does have an accident inside the house, vinegar is also effective at removing the lingering scent that could attract your dog back to the scene of the crime.
  
  

Citrus

• Dogs dislike the scent of citrus.Hemera Technologies/PhotoObjects.net/Getty Images
  
  The smell of lemon or orange is pleasant for most humans, but distasteful to dogs. Citrus is a mild natural dog repellent, and you will need to reapply frequently. You can cut up citrus fruit and place around the garden wherever you want to prevent digging, urinating, or damage to plants. Inside the house, use a mild lemon spray to keep Fido from visiting rooms where you would prefer he stay out.
  
  

Rubbing Alcohol

• Rubbing alcohol discourages dogs from visiting your lawn.Thinkstock Images/Comstock/Getty Images
  
  Rubbing alcohol is another scent that dogs dislike, and find irritating to their sensitive noses. An effective disinfectant, you can use rubbing alcohol as part of your cleaning routine, while also discouraging your dog from visiting the treated area. Mix with water as a spray to treat furniture or carpets. For a backyard deterrent, soak coffee filters in rubbing alcohol, and then allow to dry. Cut the dried filters into small slivers, and place outdoors in flowerbeds, around the lawn, or other areas you want to protect from trespassing dogs.