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Dog Skin Parasite: Dogs and Fleas

Overview

Fleas are the most common skin parasite that affects dogs. They can cause a skin allergy called canine flea allergy dermatitis (FAD) which as the name implies is an allergic reaction. Even if you believe your dog does not have fleas due to a clean home or indoor lifestyle, they could have been brought into the home by another dog or unsuspecting human. Skin reactions are an allergic reaction to flea salivary proteins injected into the skin of the dog during feeding. Ingesting a flea can lead to problems such as tapeworm.

While fleas can be seen with the naked eye, they are good at hiding out of sight. The easiest way to detect fleas is to use a fine-toothed flea comb and note if you see black and white specks which are the eggs and feces. It looks like a combination of salt (eggs) and pepper (flea feces). A quick tip is to comb any black flecks onto a damp paper towel. If you crush the specks and see red, which confirms the presence of blood, then you have confirmed the presence of fleas. Prime locations to spot fleas are on the stomach and base of the tail.

dog skin parasites fleas skin reaction
Dog Flea Bite Allergy Dermatitis Reaction on Abdomen
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Relative to their size, fleas consume a signification amount of blood. A severe infestation can cause anemia or death in puppies if left untreated.

Dog Flea Podcast

This podcast on by Dr. Bernadine Cruz from the American Veterinary Medical Association provides an excellent over on dogs and fleas, treatment and prevention.

Symptoms of Fleas on Dogs

Symptoms of a canine flea dog parasite skin problem are typically a combination of bumps and pimples. Skin reactions occur either right after being bitten by a flea or they have a delayed reaction in 1 to 2 days.  Fleas start feeding within 5 minutes of finding a host. A dog can also have an immediate and delayed skin reaction at the same time. The size of the skin reaction depends on the hypersensitivity of the dog to the flea bite antigen and the amount of antigen injected into the skin by the parasite.

Flea bites are usually found on the rear, under the legs, tail and belly. Canine flea Symptoms usually start at the tail and rump (rear end).  Itching can cause secondary problems hair loss and dry skin.  A dog with fleas will be act like it is uncomfortable, resulting in the dog trying to chew, scratch and lick affected areas.  This in turn will create secondary dog flea symptoms such as broken hairs, discolored hair that is brown in color, alopecia (hair loss),  areas of red skin (erythema),  discolored skin, skin scaling, firm skin bumps (papules), and papules that have opened, which are then crust covered.

If you only see these types of symptoms on the rear half of your dog, fleas are the most likely cause.

Diagnosis of Flea Hypersensitivity

A veterinarian will take a dogs history, look for visible symptoms such actual fleas, and flea feces in addition to specific skin tests.  The veterinarian will also differentiate this condition from other possible causes of the dog skin condition.

Flea Lifecycle

When a flea lands on a dog they will start feeding. They produce eggs after 36 hours to 2 days. A female flea produces 40 to 50 eggs a day, producing 2000 during the first 100 days. It takes 12 to 14 days for a flea to go from egg to adult. Most fleas on a dog are actually in the form of an egg, adults are estimated to be about 5% of the total population.

When a flea lays eggs on a dog they fall off and land in areas where the dog lives, such as on a bed or where the pet eats. Flea eggs will hatch in 1 to 10 days on each surface, and then move around the home into places away from light such as deep into carpets, under furniture etc. In 5 to 10 days they grow into adulthood and produce a cocoon which protects them from the environment. They can last in the cocoon for up to 50 weeks. When a host appears such as a dog, the fleas will leave the cocoon and jump onto the dog (or another pet). If they do not sense a host, they can live outside the cocoon for 2 weeks. If they cannot find a host, they will bite a human for food.

To interrupt the flea lifecycle it is important to kill any adult fleas and use an insect growth regulator such as a spot-on to interrupt the lifecycle. The home needs to be thoroughly cleaned to remove any problems for humans and other pets (see below).

Dog Flea Allergy Dermatitis Treatment

Treatment for dogs and fleas involves:

  1. Getting rid of fleas currently residing on a dogs body using a dip, medicated shampoo or in severe cases an oral medication provided by a veterinarian.
  2. A preventative that interrupts the flea lifecycle such as a spot-on (called an IGR or insect growth regulator)
  3. Addressing any symptoms such as itch, prevention of future canine flea problems
  4. Elimination of fleas from the dog and owners home. Whatever approach you choose, be sure to follow the manufacturers directions.
More detail on each product for dogs and fleas can be found below:

To remove fleas from the dog's body at home, owners can use a  dog flea dip combined with a herbal flea shampoo.  Dips have some residual effect to prevent fleas from returning to your dog in the short term.  Flea shampoos alone will kill fleas, but do not have a residual effect. After bathing your dog in a dip or other treatment recommended by your veterinarian, use a topical spot on to both treat and then prevent future dog flea problems (or a tablet product described below). Popular brands of dog flea medicine topical products and ingredients are:
  • Frontline Plus (fipronil) - liquid topical product that kills fleas in 24 to 48 hours.  Provides protection for 90 days and ticks for 30 days. Frontline Plus (unlike plain Frontline) also kills lice and helps to control sarcoptic mange (regular frontline just addresses fleas and ticks).  Frontline Plus is labeled for puppies under 8 weeks.  Regular Frontline should not be used with puppies under 10 weeks (check the label).  Retains effectiveness when wet.
  • Advantage (imidacloprid) - topical applied 1x per month, kills 98% to 100% fleas within 12 hours. Not to be used on puppies under 7 weeks.  A newer brand/formulation is called Advantix.
  • Revolution (selamectin) - topical 1x a month product that protects against fleas as well as heartworm, roundworms, hookworms, fleas, ticks, and mites.

These products are more expensive than lower cost brands that tend to contain permethrin, but are worth spending for. They are generally considered to be safe and should be started 1 month prior to the flea season which is usually April.  Check the manufacturers directions for all products for proper use and other precautions. For example, many of these products cannot be used within 3 days of the flea bath and puppies (usually under 10 weeks of age) have certain restrictions as well. Note that flea preventatives can take several hours to days after application, so if you see a flea, it just might mean that the product needs time to work. Be sure to apply spot-ons to the skin, not hair.

In addition to dog flea spot on topical preparations, there are also different tablet based products that can help with dogs and fleas. To speed healing in cases where there is a more severe dog parasite skin flea infestation, a veterinarian might recommend Capstar tablets (Nitenpyram).  Capstar comes in a tablet form and immediately kills fleas on the dogs body. The pills start working in 15 to 30 minutes, with over 90% eliminated in 24 hours (used in dogs that are older than 4 weeks).  It is often used in combination with a longer term preventative such as the spot ons Revolution/Frontline Plus.  Pills such as Sentinel (lufenuron plus milbemycin, also a preventative for heartworm) or Program (lufenuron - very popular) are given to a dog 1x per month with food, and are known as IGRs or insect growth regulators. This means that they don't kill adult fleas, but prevent the flea larvae from becoming a pupea (the stage before adulthood, thereby interrupting the flea lifecycle).  These are available with a prescription and take from 30 to 60 days to fully work as the flea fully work as a complete preventative (existing adult fleas die and larvae are prevented from becoming adults).  These are used as an alternative to spot ons.

Do not apply a spot-on immediately after bathing, since it will greatly reduce the effectiveness of the products. Follow manufacturers directions which usually call for waiting 2 to 3 days. Also check the directions for how soon you can bathe a dog after spot-on treatment (also usually 2 to 3 days).

To naturally address any itching, a product such as Allergy Itch Ease could bring some relief for any suffering related to dogs and fleas.

For more information on this dog parasite skin see our guide to dog flea medicine. Note that flea home remedies such as brewer's yeast, ultrasonic flea collars, sulfur and garlic are not effective at killing and eliminating fleas.

We do not recommend the use of dog flea collars or any type of collar for dog parasite skin prevention as these can get caught on objects and harm the dog.

Why Efforts to Get Rid of Fleas Might Fail

There are several reasons why flea treatment might not work. If this is the case, review this checklist for proper dogs and fleas treatment:
  • Did you treat all pets and dogs in your house? Since fleas spread from host to host, it's important to make sure that all dogs (cats, animals) are flea free.
  • Did you apply treatments consistently without missing any applications?
  • Did you follow the manufacturers directions?
  • Did you buy cheaper lesser known over the counter spot-ons that may not be as effective?
  • Did you thoroughly clean your dog's environment, including bedding and carpeting (see below).

Prevention and Removal of Fleas In The House

In addition to using a spot-on such as Revolution for dogs and fleas, a dogs environment should also be disinfected to ensure that all fleas are gone and kept from reinvesting the dog.  This can be accomplished with a quality disinfectant such as Benzarid and by a complete vacuuming of the affected areas.  It is a good idea to repeat treatment after 3 to 4 weeks. To remove fleas from carpets use a product such as Flea Busters.

Products such as Mineral Salts, Borax and Fossil Dust (diatomaceious earth) will help to kill both larvae and flea eggs in a dogs environment, but not adults (don't use if you also have a cat). Because of this they will take some time to work. These are not necessary if you use the Benzarid combined with vacuuming the home.

References for Dogs and Fleas

How do i treat fleas and other parasites
Dr. Chiara Noli, DVM, Dip ECVD
Ospedale Veterinario Cuneese, Borgo San Dalmazzo (CN) - Italy


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