A Guide to a Skin Workup

So you have an itchy dog, now what?

Firstly, the cause of the itchiness can be vast, anything from fleas, food, environmental factors such as pollen, dust etc. as well as mites, bacterial infections, fungal infections and many more.

So, how do you and your veterinarian go about diagnosing them?

The answer is complicated. A systematic plan is needed as often, to get to the inciting cause, the others have to be ruled out one by one. Unfortunately, this can be a costly business and can take some time so be prepared for the long haul if you want to reach the final diagnosis.

FIRST CONSULTATION
Some of the questions the veterinarian might ask you at your first appointment:

- When did it start?
- Where is the dog itchy? How extensive is it?
- Does the itchiness appear to occur seasonally? If it is strictly seasonal then it most likely Atopy.
- Did the dog develop a rash or other lesion before it became itchy or was it itchy first?
- What medications have you tried and have any of them been effective? If so, how effective where they?
- What food is your dog on? What treats etc.? (remember that some medications such as Rimadyl and dog toothpaste etc. are flavoured so count them in)
- Any other animals in the house? If so, are any of the other animals affected?
- Any humans affected?

Then, the vet should thoroughly examine your dog and perform a variety of tests:

Scrapes:
A skin scrape is done by placing a small drop of oil (usually technical oil from a microscope) and then carefully scraping the dogs fur with a scalpel blade. The material collected is then put on a slide and the vet will examine it under a microscope. Both superficial skin scrapes and deep skin scrapes need to be made. Superficial skin scrapes are predominately used to diagnosis Sarcoptic mange/Scabies whilst deep skin scrapes are used to diagnosis Demodex mange. The vet will also look for bacteria and yeast.

Hair Plucks
The vet will pluck a few pieces of hair and place them on a slide. The vet will examine the slide and look for any bacteria, fungi or mites that effect the hair follicle.
Hair plucks can also be cultured for the causative organisms of ringworm.

Ear swab
The veterinarian will take a Q tip and gently move it around inside your dog’s ear. The Q tip is then rolled onto a slide and examined. The same process is repeated on the other ear. The vet will be looking for bacteria, fungi and ear mites.

Impression smear
For an impression smear, the vet might squeeze your dog’s skin first, especially if any of the affected areas look ‘wet’ and then press a slide against the skin and look at this slide under the microscope. The vet will be looking for the presence of inflammatory cells, bacteria and fungi.

Tape tests
A piece of sticky tape/scotch tape is placed on the dog’s skin (often between the toes) and then stuck onto a microscope slide. The vet will be looking for bacteria and fungi.

Comb for fleas/flea dirt (depending on the history)
Using a very fine toothed comb, the vet will comb through the dog’s hair looking for evidence of fleas or flea dirt (looks like very small brown dirt).

Woodslamp (often not done)
One of the organisms that causes ringworm in dogs – Microsporum canis – can be detected using a Wood’s lamp. With the lights off, the vet will shine a UV light over the dogs skin. The Microsporum canis will fluoresce.

Your vet might not perform all of these tests, it will depend on a case by case basis. NB: A vet cannot say if you dog has mange or which type of mange just by looking at it. Yes, most mange has a very distinct appearance, however a scrape needs to be done to determine which type of mange and to confirm if it is in fact mange.

Usually, the initial therapy following the first consultation is usually the same:

Flea control:
A flea allergy will usually affect the skin over the dog’s back just in front of its tail, base of the tail, thighs, groin and the belly.

If flea control is not currently used or seems to be ineffective (presence of fleas/flea dirt), begin treating, normally using a monthly spot on treatment. If the infestation is severe, other environmental treatments might be needed. Remember, ALL animals in the house will need to be treated.

Commonly used products include: Revolution, Advocate, Frontline, Fibrotec (same active ingredient as Frontline), Exspot, Advantage, Advantix.

External Ear Inflammation:
If the ear is inflamed, it must be treated. If it is mild, twice weekly cleaning with a product such as Epi-otic might be sufficient but if it’s severe, your veterinarians might need to put your dog under general anaesthetic for a thorough rinse and flush. Often your veterinarian will take a sample from the ear canal using a sterile ear bud for bacterial culture in order to choose the right antibiotic.

Commonly used products: To clean the ear – Epi-otic, for infections: Otomax, Surolan,

Secondary infections:
Aggressive treatment of any infection be it bacterial or fungal infection. For superficial bacterial infections, topical shampoos may be sufficient. Shampoos such as Pyoderm, Pyostat or containing benzoyl peroxide, chlorhexidine and oatmeal. If the infection is more severe, systemic antibiotics are usually given at a higher dose than for normal antibiotics (1.5-3x higher) and for longer (often for 10-21days). For fungal infections, either topical (usually) or systemic treatment is needed depending on whether it is focal or generalised.

Commonly used antibiotics: cephalexin (Ranceph), clindamycin, potentiated sulphonamides (Purbac),amoxicillin-clavulanic acid (Synulox).

Commonly used antifungals: Shampoos containing chlorhexidine and a specific antifungal such as ketoconazole (Niz shampoo), enilconazole (Imaverol), miconazole, clotrimazole etc.

Treatment of Sarcoptic mange – NB. Sarcoptes can be transmitted to people
Treatment of Sarcoptes if suspected – unfortunately Sarcoptes can be difficult to pick up on a skin scrape so if the dog has lesions typical of Sarcoptes, which are high itchy and do not respond to steroid therapy, veterinarians might initiate treatment – in SA, Ivermectin (either injectable or oral) is commonly used or else monthly treatment with Revolution or Advocate can be used.

Additional treatment
Soothing shampoos such as Episoothe which contains oatmeal as well as antihistamines or a very short dose of Prednisolone (3 days).

Commonly used antihistamines: Piriton, Allergix

Note on antihistamines: Antihistamines have a profound ‘anti-itch’ effect in some dogs, whilst other dog’s seem ‘immune’ to the effects. Some dog’s also respond to different types of anthistamines. Ideally, antihistamines must be given at the beginning when the dog first shows signs of itchiness as then they are most likely to be effective.

SECOND CONSULTATION
The vet might ask you to schedule a follow up appointment anywhere from 10 days to 3 weeks. Some of the questions the vet might ask you at your second appointment:

- How bad is the dog’s skin still?
- How easy was it to give your dog its medication? Did you miss any doses/treaments/pills?
- Did you dog respond to the treatment? If so, how much did it respond e.g. a little better, complete response etc.
-When did the symptoms disappear or when did they reappear?

The vet might then repeat the tests mentioned earlier.
Why? You might feel like it is a waste of money for the vet to repeat the tests, but if the dog’s skin was badly inflamed or infected, the original tests might not have given an indication as to the true or initial cause of the problem. Now that the infection and pyoderma has cleared up, a clear picture might be seen.

Food trial
Depending on how your dog responded, usually the vet will place your dog on either a hydrolysed protein diet or a novel protein diet.

A hydrolysed protein diet means that the protein particles in the food are too small to elicit an allergic response. However, this diets are often not palatable or some consider them to offer a poorer protein source. For a dog that has been exposed or reacted to a lot of protein and carbohydrate sources, a hydrolysed diet might be the answer. A common hydrolysed diet is Hills z/d.

A novel protein diet means placing your dog on a diet composed of a novel protein and carbohydrate diet. The novel proteins for dogs are usually venison, fish and duck and a commonly used novel carbohydrate is potato or rice.
There are a few things to remember when doing a food trial. Once, think of your dog’s current food/diet and choose an appropriate novel diet – e.g. if you dog has been fed chicken, then try switch to fish or venison as he or she might still react to duck, the same goes for the carbohydrate source – if you dog regularly gets rice, go for potato instead. The novel protein diet can be either homemade or commercially bought.

NB: Be aware of foods that claim to be hypoallergenic because they contain no preservatives etc. It is usually (not always but in most cases) the protein and /or the carbohydrate that the dog reacts to. If a supposedly ‘hypoallergenic’ diet contains chicken etc. it is unlikely to be a good choice.
It is important that you feed your dog only its hypoallergenic/hydrolysed diet for at least 8-12 weeks. This means NO treats, no chews like rawhide or stag bars, no medication that is palatable e.g. Rimadyl etc.

If your dog responds to the food diet, then it most likely a food allergy. You can continue on the food and slowly introduce foods one at a time to see if you dog is allergic to them. Some dogs will also be fine on a raw diet.

Atopy
If your dog did not respond, then most likely your dog has atopy. Atopy is an allergy that your dog develops due to an environmental stimulus. If your dog has atopy, you veterinarian might suggest intradermal testing, RAST/ELISA tests etc. to try and narrow down what your dog is allergic to e.g. dust mites, grass etc. Then a hyposensitisation trail or avoidance of the allergen e.g. keep your dog off grass as much as possible, wipe him down after contact with grass etc. or lifelong medical treatment. Two drugs are commonly used - cyclosporine (fewer side effects) or prednisolone (NOT recommended due to the numerous side effects). Some dogs might only need avoidance and the occasional antihistamine to control their allergies.

I hope this is helpful, sorry its so long! Please also let me know of other commonly used drugs etc. in the UK as I'm mainly familiar with the ones in SA.

Any questions, problems, suggestions, corrections etc. please let me know and I'll update it.

Edit, I also wanted to put in some pictures but not sure of the forums policy of posting pictures found on Google?

Thanks for the post

Would it be OK to change this to a sticky, it may get lost otherwise ???