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What are Hair Loss Related to Parasites?

Parasites can be transmitted in boarding kennels, dog parks, grooming facilities, dog friendly facilities and shelters. Some parasites are zoonotic, which means they can be transmitted from an infected animal to humans.

External and internal parasites can cause other very serious conditions such as internal bleeding, anemia, and bacterial infection and can even be fatal.  If your dog is experiencing hair loss it is important to take him to the veterinarian.  The veterinarian will be able to diagnose the underlying cause for alopecia.

Parasites are organisms that live in or on a host to obtain their nourishment and to reproduce.  The infestation of external parasites in dogs can cause the dog to scratch, bite and chew at his skin, which in turn, leads to hair loss.  Internal parasites can cause malnutrition in dogs, which can also lead to hair loss. Hair loss in dogs is also referred to as alopecia.

Symptoms of Hair Loss Related to Parasites in Dogs

Symptoms of hair loss related to external parasites:

  • Hair loss
  • Itching
  • Scratching
  • Chewing at skin
  • Red skin
  • Lesions
  • Scaling
  • Dull coat
  • Depression
  • Visually seeing the parasites and/or eggs on the dog’s skin and fur.
  • Pustules
  • Flea feces appear like black specks, which turn red when moistened.
  • Hot spots (moist dermatitis) - inflamed and infected skin

  • Secondary bacterial infection

Symptoms of hair loss related to internal parasites may also include:

  • Scooting his bottom 
  • Vomiting
  • Weight loss
  • Diarrhea
  • Distended abdomen 


  • External parasites are parasites which live on the dog’s skin and/or hair follicles
  • Internal parasites are parasites, which reside inside a dog’s gastrointestinal tract


Causes of Hair Loss Related to Parasites in Dogs

External parasites which can lead to hair loss:

  • Fleas - Fleas live by ingesting the blood of the host and the saliva of the flea causes the skin to get itchy; flea bite allergy is the most common allergen in dogs and cats

  • Ticks - Ticks are arachnids that feed on the blood of mammals; ticks do not only cause hair loss but can cause other serious conditions
  • Mites - Canine scabies or mange in dogs are caused by microscopic mites; with demodex mange the parasite lives in the hair follicle, with canine scabies (Sarcoptic mange) the mites live on the dog’s skin

  • Most types of mange can lead to hair loss

Internal parasites which can lead to hair loss: 

  • Giardia - Giardia is a single cell organism, which can damage the lining of the intestines and reduce the absorption of nutrients; Giardia causes malnutrition which then leads to hair loss

  • Hookworms - Hookworms are parasites that attach to the dog’s intestinal lining, causing internal bleeding and malnutrition
  • Tapeworms - Tapeworms are usually visible in the dog’s stool and sometimes are attached to the dog’s anus; tapeworms are usually acquired from flea bites



Diagnosis of Hair Loss Related to Parasites in Dogs

The veterinarian will want to know when the hair loss first started and whether other symptoms accompany the condition. He will perform a physical exam on the patient to look for clinical signs of hair loss that may easily present. The dog’s weight, temperature, pulse and blood pressure may be taken as well as a check of the dog’s gums, tongue and eye tissue color.  The dog’s skin and fur will be examined. If fleas and ticks are present, they can often be visually seen on the dog. 

The veterinarian may suggest a complete blood count and a serum chemistry panel.  The complete blood count can help detect if the dog has a bacterial infection, is anemic and can also help determine the dog’s overall health.  A serum chemistry panel assesses organ function in the body.  The veterinarian may take a skin scrape and a blood smear to be viewed under a microscope.  He may also recommend a urinalysis and a fecal exam.



Treatment of Hair Loss Related to Parasites in Dogs

Treatment for the hair loss and elimination of the pest will depend on what parasite was diagnosed. Flea and tick infestation will be treated with medicated shampoo and the application of a preventative medication (such as  Frontline or Advantage). Mites may be treated with medicated shampoo/dip and Ivermectin. Your house and yard will need to be be treated for the parasites as well.  Your dog’s bedding and cloth toys should be washed in hot water.  The use of a fogger or a professional exterminator may be necessary. Internal parasites are treated with deworming medication and in this case, the yard and house will also need to be cleaned and sprayed.  

If there are other dogs and/or cats in the household they too should be treated for the diagnosed parasite with guidance from your veterinarian. De-wormers and preventative flea and tick medication are different in dogs and cats.  Dosage is weight applicable and in addition, using a canine medication and dosage on a cat can be fatal to a feline.

Dogs diagnosed with anemia will need to have B12 injections.  Patients that were malnourished will need dietary supplements and vitamins. Your dog may need to wear an E-collar so he does not keep biting or chewing at his skin.

The veterinarian may also prescribe a soothing antibiotic cream or ointment, antihistamines and anti-inflammatory medication as further treatment. Dogs with a bacterial infection will be given oral antibiotics.  Essential fatty acid, Vitamin D, melatonin supplements and salmon oil can be beneficial to help with new hair growth.



Recovery of Hair Loss Related to Parasites in Dogs

Most dogs diagnosed and treated for parasites have a good recovery prognosis.  Your dog’s hair may take weeks or months to grow back.  If your companion has had extensive skin scarring, hair growth may be limited.  It is important to follow the treatment plan and to keep your pet on a flea and tick preventative. In the event of an internal parasitic infestation, your veterinarian may decide that your dog needs a second treatment in order to eradicate the pest.  Follow up visits will be required to monitor the progress.



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Hair Loss Related to Parasites Questions and Advice from Veterinary Professionals

Need pet health advice? Ask a vet


Ask a Vet






1 Year


Moderate severity


0 found helpful


Moderate severity

Has Symptoms

Bites, Hairlss, Itchiness

How can I help my Chihuahua's hair loss and swollen bites from several small ticks that I removed from around his neck? They were actually embedded into his skin and he has severe hair loss. Please give me some insight. Thank you

Feb. 26, 2018

Ney's Owner


Dr. Michele K. DVM


1611 Recommendations

Thank you for your email. Without seeing Ney, I can't comment on the wounds, or what treatment he might need. Ticks can cause mild to severe inflammation, and there may be a bacterial infection or other parasites occurring as well. It would be best to have him seen by your veterinarian, as they will be able to look at him, determine what might be going on, and get him appropriate therapy so that his skin problems resolve. They can also recommend flea and tick prevention for him. I hope that he does well.

Feb. 26, 2018

I have a friend who has a dog like the picture. Can't afford the vet. How can I help? Anything over the counter?

May 4, 2018

Lisa F.

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