Tag Archives: dermatology

Symptoms and Root Causes – Itching, Ears, and Skin

If I had to pin down the most commonly seen problems in our practice, I’d choose itching/ear infections for the “Top 5” list. We could spend an eternity talking about these problems, but I’d like to try to offer a brief introduction to the deeper reasons for these things to happen. We’ll have to start by defining the things that we can see on a physical exam (the stuff you notice at home); and then the underlying reason they’re happening.

Symptoms: shaking of the head, scratching ears, foul smell, goopy waxy discharge (brown or yellow or pus) in the ears, swelling/redness of the ear, major swelling of the ear flap.
800px Ear infection in cocker spaniel

What’s happening: ear infection, called otitis externa. It’s generally caused by inflammation of the skin in the ear canal, which makes the skin susceptible to an infection by bacteria and yeast.

Symptoms : licking and/or chewing at the feet, red-brown staining of the fur on the feet, redness/swelling of the skin between the toes, swelling of the feet.

What’s happening: skin infection, called dermatitis, usually caused by bacteria and yeast infections. The skin is itchy, which is why dogs chew/lick.
Picture 240

Symptoms: hair loss, itching, flaky skin, red skin, rashes on the belly/armpits/groin, bad smell, oily/dull/dry coat, peeling skin, crusty skin, or wet/sticky ulcers on the skin surface.

What’s happening: skin infection, usually by bacteria and sometimes yeast, because of inflamed skin surface.
Malassezia dermatitis

In summary, dogs will have nasty ears, nasty skin, and ITCHING. It’s usually these things that drive an owner to call and make an appointment. It may be bad enough for an owner to lose sleep thanks to the licking or scratching going on all night long. (Dogs and cats both may also have gastrointestinal signs like vomiting and diarrhea from certain type of allergies.)

I’ll come right to the point. These signs and symptoms are NOT the underlying disease! We can treat the ears, feet, and skin with all sorts of different things. Ultimately, though, we’re just applying a bandaid that never really addresses the reason the dog is suffering these problems. We can provide temporary relief, up to a point.

The most common underlying cause of these chronic problems is an allergy. It’s not very common for dogs to have an anaphylactic response to something they’re allergic to. People who are allergic to shellfish, for example, will have swelling of the throat and go into shock if they eat shellfish. Thankfully, dogs don’t usually have such a violent response to an allergen. Pets can be allergic to things in the environment, or ingredients in their food.

With environmental allergies, we should think of the things that cause “hay fever” in people: pollen from trees/grass/weeds, dust, dust mites, molds. Dogs don’t get itchy/red eyes and runny noses as often as people do. They have all of those inflammatory reactions in their skin surface, which includes the ears and feet.

The other type of allergy that can cause trouble is a reaction to an ingredient in a dog’s food. The brand doesn’t matter, but the ingredients do! Corn, wheat, beef, poultry, and pork are very common ingredients in various types of dog food. Even a dog that has been eating the same food for several years can develop an allergy to the ingredients in the food. The brand doesn’t matter — the contents do.

Treating the allergy itself requires some testing to know exactly which allergy we’re dealing with. Some unlucky pets have both types of allergy (food and environmental). Thankfully, if we identify at least one of the allergy types, we can usually manage these pets successfully.

Testing for food allergy requires a special diet trial that lasts 8-12 weeks. Testing for environmental allergies requires either blood test or a skin test. THe skin test is much like the skin test that people get. Small injections are given in the skin, and the size of the red swollen area is measured to judge the response to the particular allergen that has been injected.

Treatment of an allergy consists of two major parts. First, we have to deal with the secondary effects of the allergy. This means treating the ear and/or skin infection aggressively. We may also need to control itching. Secondly, we need to treat the allergy itself. If we know what a pet is allergic to, we can treat that allergy directly. That’s the keystone!

Next week, I’ll start breaking down each type of allergy for a more in-depth look. In the meantime, how many of you have pets with chronic skin or ear problems?



Filed under dermatology, medicine

Itch, Itch, Itch : Seasonal Allergies

Spring is here, more or less. We got an early preview a while back that threw off the usual calendar, but the plants and trees have inched their way through colder temps since then. Early in the warm season, trees in particular are throwing pollen into the air. Other plants do as well, and depending on the month, different types of plans will release pollen throughout the growing season. Mid-summer tends to be a mix from grasses, with trees and weeds as well. Late summer and early fall are mainly weeds. All of this pollen is a bane for anyone with hayfever or asthma. (Believe me, I know this wholeheartedly — my hayfever gradually gets worse each year.) Itchy eyes, congestion, a sore throat — all of it’s part and parcel for breathing in the pollens carried around by the wind outside. Without the help of antihistamines, steroid nasal sprays, inhalers, and allergy shots, people would be utterly miserable. Pollen.com has a nice daily map for allergen counts.
Usa map

Dogs and cats suffer from this type of allergy, too. There’s really no difference in how the immune system is behaving in response to exposure to all of this pollen. The unique part about allergies in dogs and cats is that they do a majority of the immune-related chemistry in their skin. Instead of the respiratory problems that people get, dogs and cats will get itchy, inflamed skin. When the allergy is to the things in the environment, it’s officially called “atopy.” On a quick side note, cats can get plain old asthma; and dogs can get allergic airway disease, too. I’m not going to cover those today, as they’re separate enough as topics to make up a whole other post.

When we are exposed to things that are not from our own body, the immune system has to identify these ‘foreign’ things and decide how to respond to them. This is the basic principle we discussed way, way back in the vaccine posts. (Immune Basics & Immune Responses) You’ll remember that we have to stimulate the immune system more than once in order for it to produce a good response from vaccination. The seasonal changes in pollen end up working much the same way. In this case, it’s an unfortunate turn of events. Young animals are exposed to all of these pollens during the first year of their life. This is a lot like the first vaccination. The immune system catalogs and learns the foreign material (pollens). Then, we go through winter with relatively low exposure. The next year, when the growing season begins, the immune system once again is exposed to these foreign materials. The problem is that the immune system often overreacts to this second exposure, and releases all kinds of pro-inflammatory chemicals that lead to redness and itching. The things that follow for allergy-suffering pets stem from that overreaction. Just as not all people suffer from allergies, not all dogs and cats do. We believe there is some genetic component, but the real reason for allergies developing isn’t understood.
512px Mast cells
Usually, I see a gradually increasing severity of signs and symptoms in dogs and cats. The first ‘bad’ year is just a little itching and licking here and there. Each year, the allergies get progressively worse, with more licking and itching, maybe a hot spot. Things get ugly from there: large hot spots, skin infections, hair loss, claw/toenail infections, and ear infections. It’s shocking sometimes to see how bad something as simple as a little pollen allergy can get.

Common clinical signs and history that we see include:
•Licking the feet or chewing the feet
•Redness of the feet, belly, and ears
•Licking/chewing/scratching at various areas on the skin
•Hair loss
•Flaking/peeling skin
•Hotspots – areas of moist, red, gooey skin and partial hair loss; these are painful
•Ear infections (not as common with this type of allergy but sometimes seen)

800px Chronic allergic otitis dog
When I first see a pet with mild signs, I will go over with the owner when the problems first started. Usually, owners will realize that there was a -little- itchiness in the prior summer. “This year it’s a lot worse” is something I commonly hear. We have to rule OUT a couple of other problems as we work on finding out about environmental allergies. Allergy to food ingredients and allergy to flea bites can also cause similar signs in pets. I’ll discuss those another time. Once we rule those out, or if the history suggests that the problem is very obviously seasonal, we have a preliminary diagnosis of Atopy — Environmental Allergies. One last quick note on the source of allergens: indoor allergens can cause atopy, too. Things like dust, dust mites, dander, etc. I’m focusing on the outdoor stuff because it’s seasonal.

Treatment for allergies is two-fold. First, I generally have to apply a set of band-aids in the form of treating the symptoms of the allergy. I have to help stop the itching, calm down the redness and inflammation, treat infections, and make sure that all external parasites have been ruled out or treated. These things don’t treat the underlying cause of the allergy, though. They help treat the symptoms. For some patients, this is “good enough” for that first couple of years. We give an antihistamine in almost all cases. Supplementing omega fatty acids helps. Sometimes, medicated shampoos or conditioners are useful. We have sprays for the skin, as well as antibiotics and – if things are really ugly – glucocorticoid steroids.

Ultimately, these bandaids aren’t enough. We have to treat the underlying cause of all of these secondary problems. Treating the allergy itself means we have to outsmart the immune system. The immune system produces a specific type of antibody that hooks up to a specific type of cell in the tissue. When allergens like pollen come in contact with these antibodies, the cells burst and release inflammatory chemicals. Repetitive low-level exposure to pollens makes more and more of these little grenade cells ready to respond at the next exposure. Left on its own, the immune system is hoist by its own petard.

What’s needed is a way to stop the pollen from ever contacting the explosive cells. This is done with allergy shots. Technically, this is called hyposensitization therapy. We allergy test dogs/cats with blood or by intradermal skin testing. Most people are familiar with the little tiny injections that the dermatologist gives you to see how big of a welt your skin makes. This allows us to put together a custom cocktail of allergens that are then made into a vaccine of sorts. The pets are treated with a series of injections of the things they’re allergic to, which creates a LOT of antibodies that circulate in the blood and tissue. What this does is create a massive standing army of antibodies that are ready to all pile onto pollen before it can contact those grenade cells and make them pop. We’ve used the immune system’s response to the allergy-causing pollen to create a defense against the pollen, which protects the pet from the inappropriate overreaction of the immune system. Neat, huh? Simply put, ‘allergy shot’ are a vaccine for allergies.

We also have a medication available for treating allergies that takes the opposite approach. Instead of using the immune system and provoking a bigger response, this drug suppresses the immune system and stops the bad chemistry from happening to begin with. This drug is a specially altered version of cyclosporine that makes the drug go to the skin more readily. The only drawbacks are that this drug is quite expensive, and many animals vomit while on it. Still, for owners that don’t feel comfortable with the allergy shots, it’s a good option. The few times I’ve used it, it’s been very helpful.
Atopica dog logo
The take-home message for the day is: if it’s itchy, treat the -underlying cause- instead of just using bandaids. Thanks for reading!


Filed under dermatology, immunology, medicine

Of Mange and Mites

I’m going to sneak in a “by request” post this week. I didn’t have an opportunity to photograph a spay procedure on Wednesday, but as soon as I can get an image set together, I’ll post that. The topic today will be “mites.” While there are a ton of different mites, I’m going to show you the three we deal with most commonly. The first two are seen primarily in dogs, and the third in cats.

Demodex (Red Mange)

Demodex mites (Demodex canis) are allays found in the skin of dogs in small numbers. They live in the hair follicles and oil glands. Humans have a couple of varieties of mites, too, that live in eyelash/eyebrow follicles. People and dogs don’t trade Demodex back and forth. Dogs generally don’t infect one another with mites, either. The body usually keeps the population under control so that there aren’t any problems. In some patients, the immune system can’t keep the mite population under control. When mites overpopulate, they damage the hair follicle. Hairs fall out, causing bald patches (usually a circular spot). These patches really aren’t itchy at first. However, the follicles are damaged and inflamed, so secondary infection sets in. This bacterial infection causes a lot of itching, swelling, scabbing, and oozing. Dogs can have these small spots spread all over the body, too. That’s called Generalized Demodicosis. Here are some pictures of the mites and the skin of an affected dog. Notice the cigar-shaped body of the mite.

Demodex Milbe adult


We diagnose Demodex taking a scraping of the skin to examine under the microscope. We apply a little mineral oil to the skin, squeeze the skin to push the mites out of the follicles, then scrape the skin with a special little spatula. We have to scrape deep enough to get some bleeding: it ensures that we’ve obtained material from inside the follicles where the mites hide. We examine that under a microscope to look for mites or mite eggs.

Demodex is treatable. The spots of hair loss can be treated with an ointment called Goodwinol. It contains a naturally substance called rotenone that kills Demodex mites. (Interestingly, rotenone is used by indigenous tribes to kill fish for food.) Dogs that have the generalized form have to have special baths/dips with a drug called amitraz. Amitraz does have some side effects: drowsiness, drooling, and loss of appetite. Most are very temporary. If they’re severe, they can be treated with an antidote. Treating generalized Demodex can take months. Some patients need to have dips forever to keep the infestation controlled. Alternative treatments include use of ivermectin or milbemycin (the ingredients in heart worm prevention) on a daily basis for 3-8 months.

Cats have their own type of Demodex. We treat much the same as in dogs. I think I’ve only seen one or two cases of this in the last 7 years at Pet Authority.

Sarcoptes (Sarcoptic Mange)

Sarcoptes scabei is a very different problem than Demodex. These mites are highly contagious, so affected animals can give mites to animals contact. Boarding facilities, kennels, groomers, and the vet’s office are common places for exposure. Two to six weeks pass before dogs show signs of infestation. The mites burrow through the skin, leaving behind substances and eggs that cause dogs to have an allergic reaction. Affected dogs are insanely itchy. They literally can’t do anything but itch and scratch and chew. Their hair falls out, the skin gets crusty, may have a rash, and both dogs and owners are miserable. The most common sites for lesions are the ears, elbows, and hocks (ankles).

Here are pictures of the mites and the skin damage they cause. That’s a red fox, which normally has a fluffy tail and bright orange hair coat. The poor guy is a mess! Dogs look this way or worse when they have scabies.

Sarcoptes scabei

We diagnose Sarcoptes by attempting a skin scrape. Scrapes are not done as deeply as when we’re looking for Demodex. Scrapes find Sarcoptes only 50% of the time. This is one of the very diseases we diagnose and treat based on the examination and history.

This is a zoonotic disease! You can catch sarcoptic mange from your dog. The rash is usually in a limited area, and as long as the dog is treated, the human infestation will go away without treatment. Sometimes people do require treatment by a dermatologist.

Treament is very easy. There are topical medications (Revolution/Selamectin), injections (ivermectin), dips (amitraz and lyme sulfur), and oral medications (milbemycin). Most patients are cured within a few weeks. We also treat patients with antihistamines and steroids to reduce the itching.

Otodectes (Ear Mites)

This mite affects cats more than dogs. Ear mites are officially named Otodectes cynotis. They live in the ears and cause intense itching. They also leave behind a very crusty, sticky black material that is distinct from other types of discharge we see in ears. These mites are highly contagious among cats and from dogs to cats or vice-versa. If a household has more than one pet, all of them need to be treated. Fleas can also carry mites and eggs from pet to pet and into the environment.

The mites are visible with an otoscope when we examine the ears. We take a q-tip sample from the ear and inspect the debris under the microscope. It’s easy to see these mites. They’re similar to the Sarcoptes mites in appearance. Thankfully, these are easy to diagnose. Here’s a picture of the mites and the ear discharge.



Otodectes are easy to treat. Topical medications (moxidectin, selamectin, ivermectin) are all very efficient at killing these mites. We to treat for 3-6 weeks. The only trouble is that these mites can live in the environment, and once in a while they are found on the animal’s body as well as in the ears. The topical medications we use for flea control work for treating mites anywhere on the body. Environmental treatment is also advised, which includes vacuuming/washing and application of an insecticide.

That’s the tour of the microscopic critters that can infest pets! It’s honestly one of the grosser things to investigate. Parasites are exceptionally good at doing what they do. In a clinical way, it’s fascinating, but it’s also enough to keep you awake at night! The best way to prevent all of these disgusting passengers on your pets is to keep them healthy and protected by a topical flea prevention and/or flea/heartworm prevention product.

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Filed under dermatology, infectious diseases, parasites, preventive care