The technicians role in veterinary dermatology (Proceedings)

Part 1- Examination and Diagnostic Tests

Any appointment for dermatology begins with the technician taking a through history of the disease. Important points to cover are the signalment (age, breed, sex), the presenting complaint (especially important to determine if pruritus is present), the age at onset and if the onset of the skin problem was sudden or slow, and if the disease is seasonal.

Other important facts to determine are where on the body the problem first begin, and what was its original appearance and/or clinical signs.

The history should then focus on the pet's environment: is the animal kept mostly/exclusively indoors or outdoors ? Does it have contact with other animals, and if so, do these animals (or the people in the household) have any skin problems? The diet of the pet (including treats and supplements should be noted, and any other medical conditions previously diagnosed or suspected.

All medications, topical therapies, over-the-counter products, herbal remedies (both past and present) given for the present disease or in the past should be listed. It is helpful if the owner is told, at the time of making the appointment, to bring in all medications, past and present, especially those used in the treatment of the current skin problem. Also, ask the owner not to bathe or wash the animal for at least 48 hours prior to examination (avoiding washing off the ‘evidence').

If the appointment is a second opinion, previous diagnostics and treatment for this problem as well as the records from the referring veterinarian should be brought in. The veterinary nurse can be especially helpful in going through the record and highlighting the important points (especially diagnostic tests and treatments). 

The physical examination should provide a detail of both the types and location of lesions. This includes changes in color (erythema [redness], hyper- or hyperpigmentation), the presence of scale (dandruff), papules (rash), pustules, or nodules, condition of the hair coat (dry, broken, absent), the mucous membranes and mucocutaneous junctions (including the nasal planum, foot pads and claws). In addition, the lymph nodes should be palpated, and the weight and overall body condition noted.

Skin Scrapings for Parasites

Skin scraping is the most commonly employed diagnostic procedure in dermatology.  The procedure is simple yet can yield much information. Skin scrapings for parasites will establish a definitive diagnosis if an organism is found Depending on the parasite, they may rule out or simply decrease the likelihood of a possible differential diagnosis. 

A flat-bladed medical spatula may be used (this is the method used by the Dermatology Service at the School of Veterinary Medicine, UC Davis: Fisherbrand* Microspatula with Flat-Ended Blade, catalogue number 21-401-20, Fisher Scientific; http://www.fisherscientific.com. Alternatively, some clinicians use a #10 blade (blades may be reused since surgical sharpness is  not required).

Scraping solution

A medium grade of mineral oil is recommended for attempted retrieval of ectoparasites as other solutions may kill the harvested ectoparasite and prevent the determination of a live/dead ratio (as utilized in demodicosis).  In addition, other solutions are irritating to the patient's skin.  Potassium hydroxide (10%) or chlorphenolac may be used as a scraping solution if dermatophytes are suspected. These solutions contain clearing agents and enhance visualization of non-pigmented arthrospores attached to hairs.  Both of these clearing solutions are highly irritating to skin and can damage microscopes.

Glass slides and coverslips - Microscopes are designed to utilize the refractivity of cover slips to enhance visualization.  In addition, cover slips can prevent clearing solutions from contacting the objectives and solubilizing the glue that secures the objective lenses!

Microscope

The microscope should have a scanning lens (4X), 10X lens, and 40X lens.

Skin scraping technique- The desired areas are clipped, if needed with an electric clipper (#40 blade) before skin scrapings. The edge of the blade is dipped in either mineral oil or a clearing solution. If a surgical blade is used, it is held between the thumb and second finger so that the index finger is free to act as a guard to prevent accidental incision or impalement.

In diseases where follicular ectoparasites are suspected (demodicosis, rhabditic dermatitis), the skin may be squeezed in an attempt to force the parasites more superficially in the follicle.  Note: the benefit of this procedure has not been substantiated. 

The spatula/scalpel blade is scraped across the skin with the blade perpendicular to the skin surface.  Scraping in the direction of hair growth will facilitate sample collection. -Skin scraping can be very superficial, primarily harvesting the stratum corneun, if dermatophytes or surface living ectoparasites such as Cheyletiella sp. are suspected.  Mites that burrow in the epidermis (sarcoptic and psoroptic mites) require deeper scraping.  Follicular mites (demodectic mites) or Pelodera sp. require a scraping that penetrates the dermal-epidermal junction.  Deep skin scraping entering the dermis is marked by capillary bleeding.

The debris obtained on the scalpel blade should be spread uniformly on a drop of the scraping solution on a glass slide to distribute the material and then covered with a coverslip. Ectoparasites should be searched for using the 4X and 10X objectives under low lighting so that partially translucent parasites are not missed.  Ectoparasite identification and differentiation is an important and relatively easily learned skill.  If dermatophytes are suspected, the 4X and 10X objectives should be used to find abnormal or thickened hairs with irregular borders.  High dry magnification (40X) is required to confirm the present of dermatophyte arthrospores. 

Note: Microscopic identification of dermatophytes is quite difficult and requires extensive training and experience.

When using the microscope at 4X and 10X to look for ectoparasites, the light source should be lowered, to potentiate contrast, thus making identification of the mites easier.

Skin Samples for Cytology

This procedure is used for the demonstration of bacteria and the yeast Malassezia sp. on the surface of the skin.

Tape Technique

Take clear [not frosted] ‘scotch' tape, push it against the affected skin several times, place it on a dry microscope slide, and then inject the area under the tape with the blue dye from a Dif-QwikR stain. Alternatively, a few drops of the blue stain could be placed on the slide first, then place the tape over it. This is then examined under scanning power to identify an area that stained well, then examined under the oil immersion objective.

Skin scraping technique

The desired areas are clipped, if needed, with an electric clipper (#40 blade) before skin scrapings. The edge of the blade is used dry (i.e. NOT dipped in any oil or solution). The spatula/scalpel blade is scraped across the skin with the blade perpendicular to the skin surface.  Scraping in the direction of hair growth will facilitate sample collection. Skin scraping for cytology is a SUPERFICIAL scrape primarily harvesting the stratum corneun. Harvested material should be spread as thinly as possible on the glass slide. Usually, it is beneficial to heat fix the specimen to the slide to prevent loss during fixation and staining.

This is then examined under scanning power to identify an area that stained well, then examined under the oil immersion objective.

When using the microscope at oil immersion to look at cytology, the light source should be raised, making identification of cells or organisms easier.

Smears of pustule contents and exudates

Smears are becoming a more commonly employed and more important diagnostic procedure in dermatology.  The procedure is rapid and relatively simple yet can yield much information.

There are several uses of smears. These include establishing the presence of organisms such as bacteria or yeast, assessing the inflammatory infiltrate present, determining the presence of acantholytic cells (seen in pemphigus and occasionally in dermatophytosis), and determining thepossibility of neoplasia.

Equipment is as above for skin scraping for cytology, plus cotton swabs  to obtain material to smear from exudates, fistulous tracts, pustules, and bullae.

Technique- material is harvested with a cotton swab or by making an impression smear directly from the lesion, spread as thinly on the glass slide, heat fix ed, stained and examined under the microscope.

Hair plucks

Affected (seemingly broken or bent) hair should be plucked, preferably with a hemostat with plastic/rubber 'protected' jaws. The hair should be placed in mineral oil, covered with a cover slip, and examined using a microscope.

Hair may be examined for:

• Demodex mites; if present, these will be found close to or 'clinging' to the proximal (toward the base) of the hair shaft.

• Broken-off distal ends. If the rest of the hair shaft looks normal, this is good evidence that theanimal is biting/chewing of the hair (i.e., the animal is pruritic, or, rarely in the case of cats, is‘behaviorally motivated' to lick excessively).

• Large 'clumps' of melanin throughout the cortex (outer portion of the hair shaft); this suggests that the dog is 'color-diluted' and when seen in combination with non-pruritic alopecia, may facilitate the diagnosis of color-diluted alopecia. Caution: some breeds, most notably the Weimeraner, are naturally color diluted, yet do not have the associated alopecia.

• Abnormal 'rotten log covered with pearls' appearance; suggestive of dermatophytosis.

• Excessive keratinaceous debris retain around the proximal end of the hair shaft, 'follicularcasting'; seen most commonly in sebaceous adenitis.

Occasionally, lice nits or Cheylletiella mite eggs may be seen attached to the hair shaft.

Aspirates for cytology

Fine needle aspirates may yield useful information in the diagnosis of skin diseases.  The procedure is relatively simple but interpretation is difficult and requires advanced training

Required equipment is similar to skin scrapings but includes disposable syringes and needles.

Aspiration technique varies considerably contingent upon the sample and the suspected disease.

Harvested material should be spread as thinly as possible on the glass slide, heat fixed, stained, and examined under oil immersion power.

Wood's lamp examination

A Wood's lamp is a specialized ultraviolet lamp used in the diagnosis of dermatophytosis to locate affected fluorescing hairs.  The procedure is relatively simple to perform, but interpretation should be cautious.

Certain dermatophytes (primarily Microsporum canis and Microsporum audouinii and occasionally M. distortum and Trichophyton schoenleinii) produce a byproduct (a tryptophan metabolite) that fluoresces a blue-green color when exposed to a specific wave length of light. Approximately 50 - 60% of M. canis will give positive fluorescence.  Because a high percentage of feline dermatophytosis is due to M. canis infection, the Wood's lamp is a more useful tool in feline dermatology.

Wood's lamp - An ultraviolet light with a wave length of 253.7nm filtered through a cobalt or nickel filter.  Wood's lamps with two ultraviolet lights and a central magnifying lens are most useful. Hand-held (battery-powered) Wood's lamps are not powerful enough to be useful.

The Wood's lamp should be turned on and allowed to warm up for 5 to 10 minutes since wave length stability and intensity are temperature dependent. The examination room should be darkened for maximum visualization. Positive fluorescence is indicated by blue-green fluorescence coating affected hairs.  Shining the Wood's lamp on a fluorescent watch dial approximates the color of true positive fluorescence.  The underlying skin and scales should not be affected.

False positive fluorescence can be seen with various medications and hair conditioners.  The skin as well as hairs fluoresce with false positive fluorescence.  Scaling or crusting may give a yellowish color which is frequently misdiagnosed as positive fluorescence.

Fungal (dermatophyte – ‘ringworm') Culture

Fungal culture is the most accurate method of diagnosing dermatophytosis in all species.

Whenever dermatophytosis is suspected, hair and scale specimens should be placed on appropriate media for fungal culture.

The area to be cultured should be gently cleansed with water.  Use clean equipment to collect samples. Material is gathered in the same method as for direct examination. Fine scales and broken hairs should be obtained.  Large crusts or tufts of hair should be avoided.Toothbrush culture (combing a new toothbrush through the hair coat) is a reliable screening tool; especially useful for carriers.

The samples may be sent to an outside laboratory for culture. Alternatively, in-house culture media may be used. A variant of the Dermatophyte Test Media (DTM) is the usual media utilized. The principle behind the media is the presence of phenol red, a pH indicator.  Before use, DTM is amber in color.  Dermatophytes utilize the protein in the media and produce alkaline metabolites that turn the media red; most saprophytic fungi and bacteria utilize the carbohydrate in the media and produce acidic metabolites which cause no color change. Remember that after using up the carbohydrates, the saprophytes will switch to protein metabolism and turn the media red.

For proper use and interpretation of DTM, several precautions need to be taken:

• The hairs and scales should be pressed into the agar but not buried.

• The cover should be loose to allow for adequate aeration.

• Incubation should be done at room temperature.

• The media should be examined daily.

• With a dermatophyte, the red color should occur at the time the colony is first visible.

• After prolonged growth, most saprophytes will eventually turn the media red.

• Dermatophytes should be fluffy, light colored colonies.

• Any colony that has a green or black coloration should be regarded as a contaminant.

• T. verrucosum does not grow on DTM, but this dermatophyte mainly is found on horses and ruminants.

Bacterial culture, identification, and sensitivity testing

Bacterial culture is fraught with difficulty in the interpretation of results.  To be meaningful, a heavy culture of an organism must be obtained from a primary lesion (usually a pustule) utilizing sterile technique.  Epidermal collarettes can be accurately (> 80% of the time) cultured by rolling a sterile culturette across the lesion. The most common bacterial skin pathogens in small animals are Staphylococcus intermedius, Staphylococcus aureus or Staphylococcusschleiferi. Because most veterinarians utilize antibiotics on an empiric basis (for the first examination, at least) the bacterial culture is usually reserved for those cases where the typical positive response to antibiotics is not present or muted.

“Sub-Gross” examination

This is examination with magnifying lens or the otoscope without a cone. This is helpful (and impressive to clients) in finding:

• Follicular papules (papules with hair shafts coming out of them) = pyoderma, dermatophytes, or demodicosis

• Epidermal collaretes (rings of epithelial tissue)

Diascopy

Useful in determining if erythema is due to vascular dilation (as occurs in allergic diseases) or to extravasation of red blood cells (as occurs in vasculitis). The theory and practice are simple: place a clear, firm substance (plastic is best for safety, but a microscope slide may be used) against the erythematous skin. If the skin blanches, the RBCs are still in the vasculature, and the pressure has sent them in to the venules. If the skin does not blanch, the RBCs are extravasated.

Skin biopsy

Skin biopsy is one of the most valuable tools in the diagnosis of skin diseases, but when, what and how to biopsy, are important to increase the chances of a skin biopsy providing beneficial information.

Most suspected or obviously neoplastic lesions should be biopsied.  In addition, any severe or persistently ulcerated or eroded skin lesion should be sampled.  A biopsy may be useful if a disease is not visually identifiable, other laboratory tests have not been diagnostic, or a disease has not responded to apparently rational therapy.  Diseases which are subtle or unusual clinically also are prime candidates for biopsy.  In difficult cases, a biopsy may help rule out other diseases even though the suspected disease may not have definitive histopathologic characteristics.  Biopsy results also may aid in prioritizing differential diagnoses.

Once skin biopsy is considered, biopsy should be performed as soon as possible since chronicity, self-trauma, and topical or systemic therapy can potentially obscure a diagnosis. Lesions biopsied within 1-2 weeks after their development are much more likely to yield diagnostic results than those that have been present for a longer period.

What to biopsy

Fully developed lesions

Usually preferred to either very early or chronic lesions.  An exception would be if a bullous autoimmune disease is suspected, as early lesions are more likely to be useful.

Smaller lesions should be removed in their entirety, or the advancing edge of a larger lesion should be selected.

Lesions without self-trauma

Self-trauma often obscures diagnostic pathologic changes.  It may be useful to biopsy lesions that the animal cannot reach. 

If multiple lesions are present, specimens that are most representative of the disease should be sampled.  If different stages of a disease are present, it may be beneficial to obtain multiple biopsy specimens.  Often 2 or 3 tissue samples provide an answer, while one solitary biopsy may not.  Most laboratories charge no more for processing and evaluating 2 or 3 samples than for a single sample.  Consequently, multiple biopsies usually are indicated.

Solitary or indolent ulcers

Focal ulceration commonly reflects extensive preceding dermal changes under the ulcer.  Consequently, the ulcer itself should be samples.  Infectious, neoplastic or collagenolytic diseases are likely causes. 

Progressive ulcerative skin disease

In multifocal or generalized ulcerative skin disease that is progressive, areas immediately adjacent to ulcers as well as ulcers, should be sampled.  Sampling ulcerated skin will provide the pathologist with a specimen of the dermis lacking the overlying epidermis.  In multifocal, generalized or rapidly extending erosive or ulcerative skin diseases, the primary disease process may have originated in the lower epidermis, at the dermal-epidermal junction, or in the superficial dermis.

Necessary instruments

 A separate cold-sterilization tray containing the necessary instruments

for performing a skin biopsy should be dedicated to this procedure.  Because delicate handling of fragile biopsy specimens is imperative, the tray should include a small pair of curved iris scissors and several pairs of fine eye forceps of various types.  Small, curved hemostats, a small needleholder and suture scissors should also be available.

Specialized instruments

Cutaneous disposable biopsy punches (4-,6-, and 8-mm) Used punches may be placed in the sterilization tray and reused 3 or 4 times.

Advantages of punch biopsy technique include ease and speed of procedure, requirement of fewer sutures (four millimeter biopsy specimens require no sutures and 6- or 8-mm biopsy specimens require only 1 or 2 sutures). 

Indications for punch biopsy include the fact that multiple specimens can be obtained easily and rapidly. Also difficult sites such as the planum nasale, footpads, and ear pinnae are more easily sampled with a biopsy punch.  These usually require general anesthesia or heavy sedation.

Advantages of wedge biopsy technique are that there is less trauma to fragile lesions such as bullae or vesicles. This method can also obtain subcutaneous fat.

Approximately 90% of the skin biopsies performed by the Dermatology Service, School of Veterinary Medicine, UC Davis are punch biopsies. Most of these are performed with local anesthesia and light sedation or physical restraint. General anesthesia is more commonly utilized in cats.

Site preparation

Haired skin biopsy sites are clipped carefully so as not to induce inflammatory artifact.  Cleansing of the site is neither recommended nor necessary.  Do not scrub the lesion or otherwise disturb any scales, crusts, or surface debris since they may offer valuable diagnostic clues.

The site is marked with an indelible marker and undermined with 1-2 ml of a 2% lidocaine and 8.4% sodium bicarbonate solution (2.5 cc of the lidocaine, 0.5 cc of the sodium bicarbonate) deposited subcutaneously using a 25 or 26 gauge needle.  One cc of the solution is generally sufficient for each skin biopsy site.  Proper anesthesia is enhanced by gently repositioning the needle several times and depositing the anesthetic in a fan-like pattern.  Since sensory nerves radiate peripherally from the spine, the recommended site of injection is the side of the biopsy site which is closest to the spinal column so that needle repositioning will not cause additional discomfort to the patient.

The biopsy specimen is obtained about 5 minutes after injection of the local anesthetic.  The indelible marker dots prevent the inadvertent sampling of non-blocked regions since the bleb of local anesthetic may no longer be visible. The punch is gently rotated in one direction until the blade has entered the subcutaneous tissue.  The punch is rotated in one direction since back and forth rotation increases the likelihood of specimen damage from shearing forces.  A sudden easing of pressure is noted when the punch has successfully entered the subcutaneous tissue.

Once the specimen has been cut free from the surrounding skin, the specimen should be removed gently by grasping the margin or the underlying subcutaneous fat with a pair of fine forceps.  If necessary, iris scissors are used to detach the subcutis.  Fresh unfixed tissue is extremely fragile.  The specimen is blotted gently on a paper towel to remove excess blood and placed with the subcutaneous side down on a small piece of wooden tongue depressor or cardboard.  Gently pressing the biopsy specimen flat facilitates adherence and allows proper anatomic orientation of the specimen in the laboratory.  Specimens with the attached "splint" are then immersed in or floated specimen-side down in the fixative.  Timely placement of the specimen in the fixative is critical, as artifactual changes may occur within one minute after the biopsy specimen is obtained. 10% neutral phosphate-buffered formalin is the fixative of choice.

Further Reading

Littlewood J: Investigative and Laboratory Techniques. In Foster AP, Foil CS (eds): BSAVA Manual of Small Animal Dermatology. BSAVA Association, Gloucestershire, pp 20-30, 2003.

Scott DW, Miller WH, Griffin CE:  Muller and Kirk's Small Animal Dermatology. 6th edition, W. B. Saunders Company, Philadelphia, pp 71-206, 2001.

Part II – Zoonoses

Zoonoses are diseases that can spread from animal to people (and vice-versa). In general, if a person feels they have been exposed to, or have a zoonosis, they should see a physician, preferably one with experience in zoonoses/infectious diseases. Description of lesions in humans are provided for completeness, and are not to be used for self-diagnosis, or as a substitute for seeking medical attention.

Dermatophytosis (‘ringworm')

These are infections caused by fungi in the Micropsorum or Trichophyton genera. M canis, M gypseum, T mentagrophtes  are the most common in the author's practice. In Europe, M persicolor must also be considered.

While the most common lesion in cats is the circular area of alopecia (the ‘ring') these organisms can cause any type of lesion, including a papular eruption, nodules on the muzzle (of dogs) and excessive scale. Clinical signs in people may also vary, but the presence of an erythematous circular eruption is suspicious. Pruritus is variable. Diagnosis in animals is as noted above. It is important to remember that dogs and cats can act as carriers without showing clinical signs.

Sporotrichosis

This is a more disease caused a yeast (Sporothrix schenkii), which in small animals usually presents as a nodular to ulcerative disease.  It is more serious because the organism can (sometimes rapidly) travel via the lymphatics to the internal organs, which makes the prognosis less favorable. The disease is more common in cats, and this species often sheds large numbers of the organisms via ulcers and in the urine. Diagnosis is by demonstrating the organism on histopathology, immunofluorescent antibody testing on affected tissues, impression smears, and/or culture.  Lesions in people frequently start as non-painful nodules on the hands, and may rapidly progress into the lymphatics. Care should be taken in handling suspected samples. Owners should minimize contact with affected animals and wear protective gloves. Immune-compromised humans (children, chemotherapy patients, AIDS) should be especially careful.

Methicillin-Resistant Staphylococcus aureus (MRSA), S intermedius (MRSI), S schleiferi (MRSS)

We are at the relative beginning of our understanding of how often these bacteria are passed between animals and their handlers (and on which one the organism actually originated). However, there seems to be little doubt that in horses and in small animals these organisms can be passed between species, especially when dealing with MRSA. In both animals and people, carrier status may be temporary. In one recent survey, veterinarians and veterinary nurses, especially those that worked with large animals, were at increased risk to carry MRSA compared to the general population. While in most cases these organisms pose little risk to healthy persons, sick pets may be at risk, especially those undergoing surgery. In confirmed cases, barrier protocols (wearing gloves and gowns specifically delineated for the patient, having a dedicated area/cage for the patient, etc) should be in place. On a day to day basis, enforcement of strict hand washing procedures between handling of all patients is important. For more information, see the current BSAVA Practice guidelines.

Pruritic ectoparasites

These include scabies (Sarcoptes scabeii - usually found in dogs), cat scabies or head mange (Notoedres cati – usually found in cats), and cheyletiellosis (Cheyletiella spp – found in dogs, cats, and rabbits). The two scabies species are usually very pruritic, while Cheyletiella may present with primarily excessive scale. All three parasites can cause a papular, pruritic rash in people. Diagnosis of S scabeii  and Cheyletiella spp can be challenging, as in some animals very few mites are needed to cause pruritus, thus they are not always seen on skin scraping. In contrast, Notoedres cati is often easy to demonstrate on skin scraping. In general, any animal exhibiting signs of these ectoparasites should be presumptively treated, along with all in-contact animals, and any people (owners, veterinarians, or nurses) with compatible signs should seek medical attention.

Further reading

Hanselman BA, Kruth SA, Rousseau J, et al. Methicillin-resistant Staphylococcus aureus colonization in veterinary personnel. Emerg Infect Dis 2006: 12:1933-1938.

MRSA: Practice Guidelines: http://www.bsava.com/resources/mrsa/mrsaguidelines

Part III –Topical treatments

Topical therapy is extremely important in the management of allergic, infectious, and seborrheic disorders. It can be used as a sole therapy or adjunctive therapy for these disorders, often minimizing the need for systemic therapy. Major developments in the last decade with many new products available with better ‘delivery systems' and active ingredients, and less adverse reactions. Topical therapy can thus have adjunctive and synergistic effects in overall management of skin diseases. The advantages are: causing a decrease in pruritus by removing allergens, decreasing microbial counts, normalizing keratinization by reducing epidermal division [keratoplastic] and increasing desquamation [keratolytic], and maintaining or replacing moisture to the skin.

The major disadvantages of topical therapy are time involved, labor intensive, cost and client and patient compliance.

In general, a definitive diagnosis should be made whenever possible – this will determine the treatment used. In addition, if a home-treatment regimen is desired, the owner's compliance must be determined.

Vehicle= delivery system that facilitates application of active ingredient. Vehicles contain ingredients to adjust the pH, stabilize the active agents, promote delivery of active agents to skin surface or into/through the stratum corneum, make the product cosmetically pleasing (e.g., fragrance).

Types of vehicles:  Shampoos, rinses/dips, creams/ointments/gels, soaks/wet dressings, powders, sprays, lotions.

• Shampoos are the most common delivery system in veterinary medicine. They both cleanse the skin, remove scale, crust, debris, allergens, microbes, as well as deliver medication to skin.

• Sustained-release microvesicle technology: Novasomes® (Vétquinol) or Spherulites® (Virbac) may enable slow-release of active ingredients.

• Bathing procedure: consider clipping hair, bathe with cool or lukewarm water (hot water → pruritus), have a contact time of 10 to 15 minutes (eg. set timer) and do not  scrub too vigorously against the hair coat, especially in short-haired dogs; this may lead to pyoderma. Also, do not use old shampoos – shampoos can act as culture media for bacteria. The frequency of baths varies with severity of lesions and owner compliance

• Rinses/Dips are concentrated solutions or powders mixed with water, commonly used alone or after shampoo, and dry on animal, not rinsed off. They leave a residual layer of agent. These are especially useful for moisturizing the skin, or for treating fungal or parasites.

• Lotions are liquids in which medicinal agents are dissolved or suspended; some are liquid powders, and may be more drying (because of their alcohol or water base); newer formulations use more propylene glycol and water with less or no alcohol. Indicated for acute exudative (oozing) dermatoses. Not commonly used.

• Creams: oil-in-water formulation; absorb water; best for localized lesions in non-haired areas (nasal planum, paws, elbows)

• Ointments: water-in-oil; most occlusive vehicle.

• Gels: clear, colorless, greaseless and rubbed into skin completely.

• Agents: active ingredient in formulation; may be more than one.

• Antibacterial: benzoyl peroxide, ethyl lactate, chlorhexidine, triclosan, silver sulfadiazine, mupirocin

• Antifungal: ketoconazole, miconazole, clotrimazole, chlorhexidine, 1% selenium sulfide, 2% acetic acid, 2% boric acid

• Keratolytic/keratoplastic: sulfur, salicylic acid, phytosphingosine (major component of ceramides, the main lipid responsible for maintaining the cohesion of the stratum corneum), coal tar (not used as much as previously)

• Antiparasitic: pyrethrins and permethrins, amitraz (for demodicosis)

• Antipruritic/anti-inflammatory: glucocorticoids, Allermyl® shampoo or spray (linoleic acid, vitamin E, l-rhamnose - VIRBAC; Duoxo® shampoo or spray (phytosphingosine and hinokitiol)- Sogeval.

• Emollients (decrease transepidermal water loss): safflower, sesame, lanolin, mineral oil

• Humectants (incorporate into statum corneum and attract water): propylene glycol, glycerin, colloidal oatmeal, urea, lactic acid

• Astringents (dry skin and decrease exudation): witch hazel (Hamamelis spp), Burrow's solution (aluminum acetate)

• Deterrents (unpleasant taste):  Bitter apple®, hot pepper spray. Variable efficacy.    

And finally

The veterinary nurse can have a tremendously positive effect on the practice in the realm of client communication by:

• Explaining and answering questions regarding the veterinarian's treatment program

• Explaining and answering questions regarding all medications and products

• Dosage intervals and appropriate administration

• Possible side effects

• Demonstrating/explaining the correct techniques for cleaning ears, shampoo  therapy, administration of oral and topical medications

• Client education handouts

• Follow up communication with clients to improve compliance and understanding