Dermatology Fact Sheets

What About Allergies?Dermatology Fact Sheets

What About Allergies?

Allergies are one of the most common causes of skin problems in dogs, cats and horses. Dogs commonly manifest allergies with itchy skin, licking repetitively at their feet and/or recurrent ear and skin infections. Horse often get hives and can be itchy and cats can lose their hair from over grooming or cause significant self trauma as a result of allergies.

The dermatologists at the Veterinary Medical Teaching Hospital work closely with owners to try and determine what their pet is allergic to and figure out the best way to tailor therapy for that animal. This often includes evaluating for any secondary infections of the skin, treating any identified infections, looking for any evidence of external parasite problems and establishing strict ectoparasite control to meet that animal's lifestyle. Elimination diet trials can determine if an animal has a food allergy and allergy testing via skin tests or blood tests can determine what should go into allergy shots for pets proven to be allergic to pollen and molds in the environment. There are many therapies available for managing animals with skin allergies and successful management often involves finding the right combination of therapies. This is something that the dermatologists at the clinic are particularly skilled at doing.

Chronic ear infections in dogs and cats may result from ongoing allergies, but there are a number of other factors that can cause chronic ear infections. The Dermatology Service staff use video otoscopy and, if needed, CT scans to better evaluate the patient with chronic ear disease.

In addition to managing animals with skin allergies, our dermatologists can diagnose and manage auto-immune skin diseases, infectious skin diseases (fungal, bacterial, mycobacterial and viral) and many forms of skin cancer. The diagnosis of many of these diseases may require that we take a sample from the skin for culture of organisms or a biopsy for analysis by a pathologist.


Fleas and Flea Allergy Dermatitis

The adult cat flea spends most of its time living on cats and dogs. Fleas lay eggs on the animals, but these eggs rapidly fall off the pets and are distributed in the parts of the environment where the pets spend most of their time. The eggs hatch into larvae which evolve into pupae (cocoons) emerging in the future as adult fleas. For one adult flea found on your pet there are at least one hundred immature fleas in the animal's environment.

Flea allergy is the most common cause of itching and scratching in the dog and cat. When the flea bites your pet, it injects a small amount of saliva into the skin. Dogs and cats can develop an allergy to this saliva and will react to it with severe itching and scratching. This itching sensation may last for up to two weeks after the last flea bites.

In the dog, the most commonly observed signs of flea allergy are: biting and scratching around the rump, tailbase, and groin area; "hot spots;" and secondary skin infections. Cats may show flea bite allergy more subtly. You may see areas of hair loss and scratching, but more often you will feel small scabs and bumps around their necks and down their backs (miliary dermatitis).

It may seem confusing to hear that your dog or cat has flea allergy dermatitis if you never see fleas. This is mainly due to the fact that your pet has a remarkable capacity to chase and subsequently eat the fleas! You may also find evidence of fleas on your pet by using a fine comb and brushing out the "flea dirt" that they leave behind. This "dirt" looks like small black dots, and is the excrement of the flea. When placed on wet paper, it dissolves in red streaks because it contains partially digested blood.

Unfortunately, there is no easy solution for flea allergy, nor is there a magical medication. The only long-term efficacious and safe therapy for flea allergy dermatitis is to keep your pet from being bitten by fleas. This may seem like an impossible task, but it is not. Remember, successful resolution of the flea-allergic animal's misery requires that the fewest number of fleas bite your pet.

The control of fleas is an ongoing process, but once started, it is not difficult to sustain. The following recommendations will help you in this control, but you should remember that they are simply guidelines. The flea control program you use must be tailored to your individual situation. Just as we are constantly updating our protocol, you will need to change yours as new products become available and the efficacy of those now in use are altered by time of year, location, and reformulation.

The products listed in this handout are some carried by the hospital pharmacy. We do not endorse any particular brand-name product. Our intention is to recommend a specific active ingredient for use, and we use the products that we stock as examples.

We recommend the use of an adulticide product for all dogs and cats in the households. The newer veterinary "spot-on" products offer both safety and convenience. These products have been shown to be very effective when used as instructed. They are not absorbed into your pet's bloodstream (they stay in the skin), making them very safe. Advantage(r) (imidacloprid), Frontline Plus(r) (fipronil and methoprene) and K9Advantix(tm) (imidacloprid and permethrin) are currently available at the Small Animal Clinic. Accurate dosage is based on the dog's weight. These products are applied by parting the hair between the shoulder blades and down the back, applying the small amount of liquid onto the skin. Application frequency varies with the product and bathing needs. These products are most often applied every 2-4 weeks. It is recommended that you apply the spot-on treatment 1-2 days after bathing. Depending on the product, fleas contacting your pet will die within 12-36 hours after exposure to the spot-on product. Frontline Plus(r), Frontline(r) Spray (fipronil) and K9Advantix(tm) are also effective for the dog tick and can safely be used on puppies older than 8 weeks. K9Advantix(tm) can be used safely on puppies 7 weeks of age and older. K9Advantix(tm) is toxic for cats and should NOT be used in households with cats. Advantage(r) can be safely used on puppies 7 weeks or older.

Revolution(r) (selamectin) is a "spot on" product that is absorbed into the body. Revolution(r) is effective against heartworms, scabies mites, and a variety of intestinal parasites as well as fleas. Revolution(r), once absorbed into the body, works on fleas by secretion onto the skin by the sebaceous glands. Revolution(r) is safe to use on puppies and kittens over 6 weeks of age.

An oral flea adulticide, Capstar(r) (nitenpyram) is also available. Capstar(r) is a very safe, short acting oral tablet which can be given daily or every other day for routine flea control, or used additionally with other products. Capstar(r) is safe to use daily, or can be used as a "rescue" drug to kill fleas should they be seen on dogs and cats older than 4 weeks and at least 2 pounds of body weight. Capstar(r) begins working within seven minutes and kills fleas immediately after the first blood meal is taken. Capstar(r) is an oral, systemic product and therefore is not affected by bathing or swimming. Most recently available is a monthly oral flea adulticide, Comfortis(tm) (spinosad). Comfortis(tm) is a chewable flavored tablet approved for use in dogs only, 14 weeks of age and older. Comfortis (tm) achieves full effectiveness within 4 hours and kills fleas immediately after the first blood meal is taken.

Two other veterinary products recently available for dogs are Vectra 3D(tm) (dinotefuran, permethrin and pyriproxyfen) and Promeris(tm) for dogs (metaflumizone and amitraz). The hospital is not yet carrying these products, but they may be available through your veterinarian or at the hospital in the future. Vectra 3D(tm) is a spot-on product safe for use on dogs and puppies 7 weeks of age and older. Vectra 3D(tm) is toxic to cats and should not be used in households with cats. This product kills and repels fleas, ticks and mosquitoes, and contains pyriproxyfen, an insect growth regulator which prevents development of flea eggs and larva. Vectra 3D(tm) is recommended for monthly application. Promeris(tm) for dogs is another topical spot on product safe for dogs and puppies only, 8 weeks of age and older. Promeris(tm) for dogs kills fleas and ticks and is effective for up to 6 weeks, though recommended for monthly application.

If you own cats, they must be involved in the flea control program even if they are not exhibiting any problems, or they will carry the fleas to your house, yard, and dogs. Cats are much more sensitive to the chemicals in flea preparations, and many insecticides cannot be used on them. We recommend Revolution(r) (selamectin), Frontline Plus(r) (fipronil and methoprene) or Advantage(r) (imidacloprid) in the feline formulation. A newer product not currently available at the clinic is Promeris(tm) (metaflumizone) for cats. Promeris(tm) for cats is safe to use on cats and kittens 8 weeks of age and older. Though recommended for monthly application, this product shows activity against fleas for up to 6 weeks. All these products are applied in a similar fashion as in dogs. Beginning at the base of the head, part the hair and spread the small amount of liquid down the top of the neck. Application also varies from two to four week intervals, depending on other treatments. Please follow the instructions outlined for your pet. Capstar(r) (nitenpyram) is also safe for use in cats as a "quick kill" in the event fleas are seen, or can be given every one to two days for routine flea control if an oral product is desirable.

Several life stages occur before a flea becomes a biting adult. Some of these juvenile stages are also targets for flea control. Decreasing the numbers of immature (juvenile) fleas is an excellent way to help prevent adult fleas and their bites. Recent research has led to the release of several products that interrupt the life cycle of the flea. Often these products are used in combination to quickly and effectively decrease the flea burden of your pet. Synthetic juvenile flea growth hormone imitators are found in many flea products. Methoprene (Precor(r)) is contained in Frontline Plus(r) as well as many of the indoor area treatments. Knockout(r) (pyriproxifen) is formulated in a collar for cats and dogs that contains a similar flea growth regulator and is effective for 13 months. Unlike other flea collars, these destroy only the young stages and are quite effective and convenient. Knockout flea spray (for dogs only) contains a synthetic pyrethroid plus pyriproxifen and can be used safely on dogs every 1-3 weeks. Vectra 3D(tm) also contains pyriproxyfen as one of its active ingredients. All of these synthetic hormones are very safe to use on animals and around humans. They prevent the adult female flea from laying viable eggs and prevent immature fleas from developing into adults.

Program(r) (Lufenuron) is an oral chewable tablet available for both dogs and cats that is given monthly with food. As the adult female flea feeds on the dog or cat, the female flea lays eggs that cannot hatch and larvae that will not survive. This product is very safe, but flea-allergic animals also need protection from the biting adults. Program(r) is best used in combination with a topical flea adulticide or Capstar(r). Another formulation available is lufenuron in combination with milbemycin, a monthly heartworm preventative. This product, called Sentinel(r) is also given monthly with a full meal.

Most other forms of flea control on your pet have been scientifically shown to be ineffective. Flea shampoos will only kill the adult fleas but have virtually no residual effect, and will not prevent reinfestation once they are rinsed off. Insecticidal flea collars alone are ineffective because they are not able to sustain high enough concentrations of insecticide over the animal's entire body. Electronic flea collars, brewer's yeast, garlic, vitamin B tablets, and extracts of eucalyptus or pennyroyal, are not flea repellent, and provide no protection for your pet. Lastly, flea combs, although helpful, are similar in effect to the use of flea shampoos alone: they do not prevent reinfestation.

All flea control products are potentially toxic or may produce unexpected side effects. Toxicity may result from accidental overdose or unexpected sensitivity. Known side effects, although rare, are vomiting, diarrhea, drooling, sluggishness, weakness, or abnormal behavior. If you suspect that your animal is reacting adversely to a flea control product, stop using the product and consult your veterinarian immediately. If the reaction occurs immediately after application, the product should be rinsed off thoroughly and the animal brought to the veterinarian for evaluation. Adverse reactions may occur from minutes to days following application. Insecticides can be toxic to people; all products should be handled carefully, avoiding direct contact as much as possible. Keep all products out of the reach of children. Cats are particularly sensitive to many pesticides. Only use products labeled to be safely used on cats. If you have any questions about a product's safety, please consult your veterinarian.

House and yard treatments need to be concentrated on "source points", areas where pets spend most of their time. This typically would include the bedding and resting areas, the feeding location, etc. You can lessen the flea burden in your home by thorough vacuuming of all source points followed by disposal of the vacuum bag and by washing all animal bedding weekly in hot water and drying at high heat for twenty minutes. Steam cleaning of rugs and carpeting +/- upholstery is also helpful.

In the yard, focus on areas where your pet(s) spend most of their time. Typically, fleas survive and reproduce in shaded, moist areas with plant or organic debris (under decks, bushes, etc). Fleas do not survive or reproduce well in sunny, open areas of lawn or patio. Elimination of yard debris will be helpful in reducing flea numbers. You may choose to use a professional exterminator service for the treatment of fleas in your home and garden.