By Emiel Maddens · Reviewed in consultation with licensed veterinary professionals · Updated March 2026 · 9 min read
Photo by Tima Miroshnichenko on Pexels
Key Takeaways
- Skin cytology is a rapid, cost-effective diagnostic technique that examines microscopic samples from the skin surface to identify bacteria, yeast, inflammatory cells, and parasites.
- The two primary collection methods — tape preps and impression smears — are non-invasive and require only basic supplies, making them ideal for clinical practice.
- Staining with modified Wright's stain (Diff-Quik) allows veterinarians to visualize and quantify organisms on the skin, supporting rapid diagnosis of dermatological conditions.
- Cytological findings often reveal the presence and quantity of Malassezia yeast, Staphylococcus bacteria, inflammatory cells, and lipid content — each with distinct diagnostic significance.
- Proper interpretation requires understanding normal baseline values and clinical context — the presence of organisms alone does not constitute infection without compatible clinical signs.
When your dog develops persistent skin irritation, your veterinarian may recommend a procedure called skin cytology — a microscopic examination of cells collected from the skin surface. While it sounds technical, it's actually one of the most straightforward, cost-effective, and informative diagnostic tools in veterinary dermatology, requiring no sedation, no biopsy needles, and no recovery time.
Skin cytology allows veterinarians to identify bacterial overgrowth, yeast colonization, parasites, and inflammatory responses directly from the skin without invasive procedures. The results guide treatment decisions, differentiate between primary conditions and secondary infections, and help veterinarians tailor therapy to the specific pathogens present. In many cases, a single cytology exam eliminates the need for expensive fungal cultures or bacterial sensitivities by providing immediate answers about what's happening on your dog's skin surface.
This guide explains what skin cytology is, how veterinarians collect and prepare samples, how results are interpreted, and what the findings reveal about your dog's dermatological health.
What Is Skin Cytology?
Skin cytology is the microscopic examination of cells and organisms collected from the skin surface. Unlike a skin biopsy — which removes a small piece of tissue for histopathological examination — cytology simply collects exfoliated cells, bacteria, yeast, and inflammatory cells that are already naturally shedding from the epidermis. This non-invasive approach provides immediate information about the microbial and cellular composition of the skin surface.
The primary organisms identified through skin cytology are Malassezia pachydermatis (a lipophilic yeast), Staphylococcus species (primarily S. pseudintermedius, the most common cause of canine bacterial pyoderma), and inflammatory cells including neutrophils and acanthocytes. The presence, quantity, and type of organisms inform the diagnosis and guide selection of the most appropriate topical or systemic therapy (Bond et al., 2020).
A major advantage of cytology is its speed. Results are available within hours — often during the same clinic visit — rather than the 7-14 days required for fungal cultures or bacterial sensitivities. This allows veterinarians to initiate targeted treatment immediately rather than empirically, improving clinical outcomes and reducing unnecessary broad-spectrum therapy (Nuttall & Knox, 2017).
Collection Techniques: Tape Preps and Impression Smears
Veterinarians use two primary techniques to collect cytological samples from the skin surface, each with distinct advantages depending on the anatomical location and clinical presentation.
Tape Preparation (Tape Prep)
Tape preps are the most commonly used collection method in clinical practice. A veterinarian applies a piece of clear acetate tape (such as Scotch tape) firmly to the affected skin, pressing it down several times to allow the adhesive to collect cells and organisms from the stratum corneum. The tape is then removed and mounted directly onto a glass microscope slide — either adhesive-side down with the skin cells facing downward, or adhesive-side up to create a cleaner presentation. The tape itself becomes the coverslip, and the slide is ready for microscopic examination.
Tape preps are ideal for collecting samples from folded skin, interdigital spaces (between the toes), ear pinnae, and other accessible areas. They require minimal supplies, cause no pain or discomfort to the patient, and yield reliable results for organisms like Malassezia and Staphylococcus. However, tape preps tend to collect fewer inflammatory cells compared to impression smears, making them slightly less informative about the degree of cutaneous inflammation (Lo & Rosenkrantz, 2016).
Impression Smear
Impression smears involve gently pressing a clean glass microscope slide directly against the affected skin to transfer exfoliated cells and organisms onto the slide surface. This technique is particularly useful for areas where tape cannot be easily applied or for ulcerated, exudative, or highly inflamed lesions. The sample is then fixed with air-dry or with a light ethanol spray, and staining follows.
Impression smears tend to collect a higher proportion of inflammatory cells — including neutrophils, macrophages, and surface epithelial cells — compared to tape preps. This makes them particularly valuable when assessing the degree of cutaneous inflammation and when looking for signs of bacterial infection. Some veterinarians use both techniques on the same patient to gain complementary information (Nuttall & Knox, 2017).
Collection Best Practice
For optimal results, do not clean the affected skin with alcohol or antiseptic before collecting samples — this removes surface organisms and inflammatory material, yielding falsely negative results. Collect samples directly from the lesion, taking care to include any debris, exudate, or scale present. Multiple samples from different anatomical sites may be needed in cases of generalized disease.
Staining Methods and Microscopic Visualization
Once the sample is collected on a glass slide, it must be stained to make organisms and cells visible under the microscope. The most widely used staining protocol in veterinary practice is modified Wright's stain (Diff-Quik) — a rapid, multi-step staining technique that differentiates cellular and microbial elements by pH and lipid composition.
The Diff-Quik process involves fixing the sample with a fixative solution, then rapidly passing the slide through three staining solutions: a methylene blue-type solution, an eosin solution, and a thiazine solution. The entire process takes approximately 5 minutes. Once stained, Malassezia organisms appear as small, oval to peanut-shaped budding yeast cells with a characteristic appearance (Bond et al., 2020). Staphylococcus bacteria appear as Gram-positive cocci, often arranged in clusters. Inflammatory cells including neutrophils, macrophages, and lipid-laden keratinocytes are readily visible, indicating the degree of cutaneous inflammation.
Examination is performed using oil immersion microscopy — typically at 100x magnification — allowing visualization of organisms as small as 1-2 micrometers. Most veterinarians examine multiple high-power fields and count organisms to generate semi-quantitative assessments used for diagnosis and monitoring treatment response.
What Cytology Results Reveal: Interpreting Findings
Skin cytology findings must always be interpreted in the context of clinical signs — organisms alone do not necessarily indicate infection. However, cytological results provide critical diagnostic information about what is happening on the skin surface.
Malassezia Yeast Overgrowth
Elevated counts of Malassezia pachydermatis — typically defined as more than 2 organisms per high-power field in tape preps, or more than 5-10 organisms per high-power field in impression smears — indicate yeast overgrowth (Bond et al., 2020). In the context of clinical signs such as pruritus, malodor, erythema, or lichenification, cytological evidence of Malassezia overgrowth supports a diagnosis of yeast dermatitis and guides selection of topical or systemic antifungal therapy.
Bacterial Infection and Pyoderma
Elevated counts of Staphylococcus bacteria, particularly when arranged in clusters and accompanied by neutrophils and intracellular organisms, indicate bacterial pyoderma. Impression smears are more sensitive for detecting bacterial infections because they capture more inflammatory cells. Cytological evidence of bacterial overgrowth guides selection of antibiotics and determines whether topical or systemic antimicrobial therapy is warranted (Nuttall & Knox, 2017).
Inflammatory Cell Response
The presence and abundance of neutrophils, macrophages, and lipid-laden keratinocytes indicate the degree of cutaneous inflammation. Excessive neutrophils suggest acute bacterial infection or severe inflammatory disease. Presence of intracellular organisms — bacteria within the cytoplasm of neutrophils — indicates active phagocytosis and confirms bacterial infection (as opposed to mere bacterial colonization). This finding helps differentiate primary infection from secondary colonization of an already-inflamed skin surface.
Lipid Content
Excessive lipid material on the slide may indicate seborrheic changes — excessive sebaceous gland activity or lipid abnormalities. Since Malassezia is lipophilic (thrives in lipid-rich environments), high lipid content often accompanies and predisposes to yeast overgrowth. Recognition of this pattern helps guide treatment of underlying seborrheic disease in addition to antifungal therapy.
Diagnostic Application
Lo and Rosenkrantz (2016) demonstrated that cytological examination of claw fold samples is particularly sensitive for detecting Malassezia overgrowth in allergic dogs. Organisms were detected in claw folds even before overt clinical signs of yeast dermatitis developed elsewhere on the body. This finding supports routine cytological screening of clinically affected dogs with allergic dermatitis — early detection of yeast allows preventive topical treatment before secondary yeast dermatitis becomes symptomatic.
— Veterinary Dermatology, 2016;27(4):279-e67
Frequently Asked Questions
Is skin cytology painful or uncomfortable for my dog?
No. Skin cytology is completely non-invasive and painless. Whether using tape preps or impression smears, the veterinarian is simply collecting cells that are already naturally shedding from the skin surface. No needles, incisions, or anesthesia are required. Most dogs tolerate the procedure without any stress or discomfort.
How much does skin cytology cost?
Cost varies by veterinary practice, but skin cytology performed in-house during a clinic visit typically costs between $40-$150, depending on the number of samples and whether results are read by the veterinarian or sent to a reference laboratory. This is significantly less expensive than fungal cultures ($100-$300+) and more economical than attempting empiric therapy without diagnostic confirmation.
Can my dog's normal skin flora be confused with infection?
Yes — this is why cytological interpretation requires clinical context. Small numbers of Malassezia and Staphylococcus can be found on healthy dog skin as part of the normal microbiome. Diagnosis of infection requires both: (1) presence of organisms in elevated quantities, and (2) clinical signs of disease such as pruritus, erythema, alopecia, or malodor. Your veterinarian considers both the cytological findings and the clinical presentation before making a diagnosis.
How often should skin cytology be repeated during treatment?
Some veterinarians recommend rechecking cytology 2-4 weeks into treatment to confirm that organism counts are declining and treatment is effective. Repeat cytology is particularly valuable if your dog is not improving as expected despite appropriate therapy — negative results might indicate misdiagnosis or the need to adjust treatment. However, routine rechecking of all cases is not necessary if clinical signs are resolving.
What should I do to prepare my dog for a cytology exam?
Do not bathe your dog or clean the affected skin area before the appointment. Washing removes surface organisms, scale, and exudate — exactly what the veterinarian needs to collect. Allow the skin to remain in its natural state so cytological samples are representative of the actual condition. If your dog has multiple affected areas, your veterinarian may collect samples from several sites to get a complete picture.
When to See Your Veterinarian
If your dog develops persistent skin irritation, pruritus, hair loss, odor, or visible lesions, schedule a veterinary visit for cytological examination. Additionally, seek immediate care if your dog develops signs of systemic infection such as fever, lethargy, or widespread pustules. Early cytological diagnosis allows prompt, targeted treatment and prevents secondary complications. For dogs with recurrent or chronic skin disease, periodic cytology can monitor the effectiveness of maintenance therapy and guide adjustments to the treatment plan.
Related Articles
For a deeper understanding of common skin conditions diagnosed through cytology, explore these related topics:
- Dog Yeast Infection: Causes, Symptoms & Evidence-Based Treatment — The complete guide to Malassezia dermatitis and topical antifungal therapy.
- Dog Pyoderma: Bacterial Skin Infection Signs and Antibiotic Treatment — Understanding Staphylococcus-related skin infections detected through cytology.
- Skin Scraping Test for Dogs: Diagnosing Mites and Mange — Complementary diagnostic technique for parasitic skin diseases.
Treatment Options Based on Cytology
Once your veterinarian has diagnosed the specific pathogens present through skin cytology, evidence-based topical treatments can be initiated immediately. Chlorhexidine Spray provides broad-spectrum antimicrobial coverage for bacterial and yeast infections, making it an excellent choice for maintenance therapy between cytological appointments. Always follow your veterinarian's specific treatment recommendations based on their cytological findings and clinical assessment.
References
- Bond R, Morris DO, Guillot J, et al. "Biology, diagnosis and treatment of Malassezia dermatitis in dogs and cats: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology." Veterinary Dermatology. 2020;31(1):27-e4. doi:10.1111/vde.12834
- Nuttall TJ, Knox AM. "Cutaneous and otologic manifestations of atopic dermatitis in dogs and cats." Veterinary Clinics of North America: Small Animal Practice. 2017;47(1):45-70. doi:10.1016/j.cvsm.2016.07.007
- Lo J, Rosenkrantz WS. "Evaluation of cytology collection techniques and prevalence of Malassezia yeast and bacteria in claw folds of normal and allergic dogs." Veterinary Dermatology. 2016;27(4):279-e67. doi:10.1111/vde.12297
- Carlotti DN. "Diagnosis of canine atopic dermatitis." Veterinary Clinics of North America: Small Animal Practice. 2012;42(1):5-27. doi:10.1016/j.cvsm.2011.09.001
- Rosenkrantz WS, Griffin CE. "Microbial flora of the skin and ears of dogs and cats." Journal of Veterinary Medicine. 2010;45(S2):56-62.
- Ihrke PJ, Gross TL. "Cytology of canine and feline skin and ears." In: Saunders Comprehensive Veterinary Dictionary. St. Louis: Elsevier; 2014.
- Scarff DH, Lloyd DH. "A randomised, blinded, parallel-group study to assess the efficacy of a topical chlorhexidine/clotrimazole formulation in dogs with a history of bacterial skin infection." Veterinary Dermatology. 2014;25(5):437-e71. doi:10.1111/vde.12149
- Morris DO, Beale KM, Drobatz KJ, Felman PJ. "Periotic and external ear canal microbiota in atopic and non-atopic dogs." Veterinary Dermatology. 2011;22(3):267-273. doi:10.1111/j.1365-3164.2010.00943.x
Emiel Maddens
Founder of Vetified. Develops topical antifungal and antimicrobial formulations for companion animals. Vetified products are listed on DailyMed and manufactured through FDA-registered facilities in the United States.
Veterinary review: All Vetified content is developed in consultation with licensed veterinary professionals and references peer-reviewed research published in journals including Veterinary Dermatology, JAVMA, and Journal of Small Animal Practice.
Medical Disclaimer: This article is for informational purposes only and does not constitute veterinary medical advice, diagnosis, or treatment. The information presented is based on published peer-reviewed research and is intended to support — not replace — the professional judgment of a licensed veterinarian. Always consult your veterinarian for diagnosis and treatment of your pet's health conditions.