skin

 integumentary system

consists of the skin and its appendages, such as glands, hair, fur, wool, feathers, scales, claws, nails, and hooves. Considered one of the largest organs in the body, the integumentary system is involved in many processes

epidermis

The outermost or most superficial layer. does not contain blood vessels. The base of the epidermal layer is known as the basal layer. cells die when they reach the surface and their cytoplasm is converted to keratin. basal layer contains melanocytes

dermis or corium

composed of blood vessels, lymph vessels, nerve fibers, and accessory organs (glands and hair follicles) situated in a tight mesh of collagen strands

Sub Q layer or hypodermis

located deep to or under the dermis and is composed of connective tissue. the SQ contains a large amount of fat.

primary skin disease

caused when immune system is not functioning properly, categorized as immune mediated. atopy (allergies) are triggered by an immune response to foreign ("nonself") proteins (food, environmental toxins, microbes, etc.). Conditions such as pemphigus occur when the immune system responds to the animal's own antigen ("self"), which results in an attack of normal tissue by antibodies or lymphocytes

 Secondary skin disease

occurs when a disorder in an animal's body produces changes in the skin. These changes may or may not be characteristic of a specific disease. For example, dermatitis can be seen with liver and kidney disease, and superficial skin necrosis causing crusting, alopecia, and redness can be seen with diabetes mellitus and liver disease Alopecia and dry, thickened skin can be seen with endocrine diseases such as hypothyroidism. while skin darkening and seborrhea can be seen with other endocrine diseases such as hyperadrenocorticism. Secondary skin disease can also be caused by nutritional deficiencies such as diets with inadequate amounts of protein, fats, minerals, and some vitamins

radioallergosorbent tests (RAST)

identify atopic dermatitis (allergies) and its causes

Dermatophyte infections (dermatophytoses)

commonly referred to as ringworm infections. include the genera Microsporum, Trichophyton, and Epidermophyton. Dermatophyte organisms can live only on dead keratin tissue and can be successfully eliminated only if the infected area is free of fungi. Therapy for dermatophytosis typically involves oral and/or topical treatments for several weeks.

bacitracin: bacitracin combined with polymyxin B and neomycin: Neosporin, Mycitracin, Triple Antibiotic

inhibits cell wall synthesis, bacteriostatic or bactericidal depending on concentration; primary activity against Gram-positive bacteria. used for dermal laceration, abrasions, minor burns; ocular infections

clindamycin, clindamycin (sole agent): ClinzGard, Cleocin T, Clindamax

 inhibits bacterial protein synthesis; primary activity against anaerobic and Gram-positive aerobic bacteria. used for feline acne, localized skin infections, anal sac infusion, abscesses, surgical incisions

gentamicin gentamicin with betamethasone: Gentocin Topical Spray, Betagen Topical Spray, GentaSpray

inhibits bacterial protein synthesis; primary activity against Gram- negative aerobic bacteria. superficial bacterial skin infections, moist dermatitis (hot spots), otitis.

mupirocin

 inhibits bacterial protein synthesis; primary activity against Staphylococcus sp. and other Gram- positive bacteria. used on superficial pyoderma, skin fold pyoderma

neomycin

 inhibits bacterial protein synthesis; primary activity against Gram-negative aerobic bacteria. superficial skin infections, anal gland intusion, otitis

nitrofurazone

inhibits bacterial enzymes; bactericidal for many bacteria. superficial bacterial infections

silver sulfadiazine

disrupts microbial cell membranes and cell walls; primary activity against Gram-negative and Gram-positive bacteria including Pseudomonas sp. second and third degree burns, localized bacterial infections; otitis

polymyxin B

lyses bacterial cell Membrane. dermal laceration, abrasions, minor burns; ocular infections

Thiostrepton

 inhibits protein synthesis; primarily activity against gram positive bacteria. Superficial skin infections, anal gland infusion, otitis

Clotrimazole

inhibits production of the fungal cell wall; primary activity against dermatophytes (ineffective in cats) and yeasts. used on Bacterial and yeast skin infections, otitis

Copper naphthenate

disrupts the enzyme systems of fungi. Thrush in horses (caused by the fungus Spherophorus neaophrous)

Ketoconazole

inhibits production of the fungal cell wall; primary activity of sprays is against dermatophytes and yeasts; shampoos may also be effective against Malassezia. Dermatophytosis (use in combination with other products because minimally effective alone), topical yeast infections

Lime sulfur

forms pentathionic acid and hydrogen sulfide  after application that provides antimicrobial and antiparasitic activity. Dermatophytosis, parasitic infestations such as Demodex, sarcoptic mange, and lice. Wear gloves when applying. Can discolor porous surfaces and jewelry. Avoid eye and mucous membrane contact

Miconazole

alters fungal cell membrane permeability and interferes with mitochondrial enzymes. Dermatophytosis, topical yeast infections such as Malassezia spp

Nystatin

increases fungal cell membrane permeability. Topical yeast infections. Otitis

Terbinafine

inhibits production of the fungal cell wall. Localized Malassezia dermatitis (ineffective in cats)

Topical Anesthetics

A Nonsteroidal Topical Antipruritic Drugs. Local anesthetics inhibit the conduction of nerve impulses along sensory nerves, thereby reducing pain and pruritus. They are generally used topically to minimize discomfort associated with allergies, insect bites, and burns. Local anesthetics are poorly absorbed from intact skin but can be absorbed through damaged skin. Most topical anesthetic drugs can be recognized by the -caine ending in the name and include such agents as lidocaine and tetracaine.

lidocaine (Hexa-Caine, Dermacool, Bio-Calm and the ophthalmic agent tetracaine

 A lidocaine with prilocaine cream in the human product EMLA is used for skin anesthesia prior to painful procedures such as catheter placement

Pramoxine

a topical anesthetic that is not related to the -caine anesthetics. typically combined with other topical medications to relieve itching and pain such as in the products Pramoderm HC Spray (pramoxine with hydrocortisone) and Benasoothe Shampoo and Conditioners (pramoxine with oatmeal). Pramoxine is too irritating for ophthalmic use

Colloidal oatmeal

(oats ground into an extremely fine powder) is believed to have antipruritic and anti-inflammatory effects when applied topically. Colloidal oatmeal also coats, moisturizes, and protects skin. As the concentration of oatmeal increases in a product, its drying and antipruritic effects also increases. It is found in colloidal oatmeal shampoos such as Epi-Soothe, and DermAllay Oatmeal Shampoo.

topical antihistamines

Benasoothe shampoo and conditioner contains diphenhydramine and pramoxine. AtopiCream only contains diphendyramine

Zinc gluconate

can be used alone to treat mild pruritus or in combination with other products for treating conditions with more pronounced pruritus, mild bacterial infections, Or dry skin. Zinc has been used to treat feline acne, skin fold dermatitis, and lick dermatitis. Zinc involved in wound healing, connective tissue repair, and cell proliferation. It also has antiseptic and astringent properties. A veterinary product that contains zinc is Maxi/Guard Zn7 Derm (calamine lotion used in humans contains zinc).

Topical Glucocorticoids

effectively alleviate inflammatory clinical signs. Glucocorticoids have nonspecific anti-inflammatory and antipruritic action. Glucocorticoids also decrease swelling by maintaining the cellular integrity of capillaries, thus preventing leakage of large proteins and excessive fluid from the blood into the tissue space. When applied to the skin, they interfere with normal immune responses and reduce redness, itching, and edema. They also slow the rate of skin cell production, which may reduce scarring. damaged skin at application site may increase the amount of drug absorbed into the blood stream resulting in systemic adverse effects.

hydrocortisone

The least potent topical glucocorticoid. It is suitable for long-term topical use and is a logical first choice for patients with a large area that needs treatment or for smaller patients

 fluocinolone, isoflupredone, mometasone

Topical glucocorticoids containing a fluorine atom in their structure are among the most potent products. products should be used sparingly. The frequency of topical glucocorticoid application is tapered when the itching is controlled

Short-acting glucocorticoids

hydrocortisone and cortisone, have a duration of action of less than 12 hours

soaks and dressings

used to draw out fluid or relieve itching. ex. aluminum acetate, magnesium sulfate

Intermediate-acting glucocorticoids

including prednisone, prednisolone, triamcinolone, and methylprednisolone, have a duration of action between 12 and 36 hours

Long-acting glucocorticoids

betamethasone, flumethasone, isoflupredone, and dexamethasone, have a duration of action greater than 48 hours

Lokivetmab (Cytopoint

 is a monoclonal antibody therapy that binds the itch-producing cytokine canine IL-31 in the extracellular space, so it cannot bind its cytokine receptor on neurons in the skin and transmit the sensation of pruritus (Figure 17-6B). Lokivetmab rapidly reduces the itch associated with canine atopic dermatitis and is labeled to help reduce clinical signs associated with atopic dermatitis in dogs. It is given by SQ injection at the veterinary clinic and reduces pruritus within 24 hours, with effects that can last for four to eight weeks. When clinical signs gradually return, the dose is repeated. It can be used in dogs of all ages, including those less than 12 months of age, and has no known drug interactions. The most common adverse effect is Gl upset. Lokivetmab requires refrigeration and should be allowed to warm to room temperature prior to injection to reduce pain associated with its administration.

Staphylococcal phage lysate (SPL)  (Staphage Lysate

an immunosuppressant. a United States Department of Agriculture (USDA)-labeled immunostimulant biologic used to reduce pruritus and recurrence of superficial and deep pyodermas and related hypersensitivity reaction to Staphylococcus in dogs. SPL enhances cell-mediated immunity by increasing the ability of macrophages to inactivate Staphylococcus bacteria and stimulates production of immunologically active substances such as tumor necrosis factor and interferon. It is given as a SQ injection with a dosage that is incrementally increased weekly for 10 to 12 weeks and then continued weekly or every other week. It is recommended that dogs receiving SPL also be prescribed antibiotic drugs for the initial four to six week treatment period. Adverse effects include post vaccine-type of reactions such as fever and lethargy as well as redness, itchiness, and swelling at the injection site. It is stored refrigerated and does not contain preservative; therefore, it must be handled aseptically.

Oclacitinib (Apoquel

approved for the control of atopic dermatitis and associated pruritus in dogs at least 12 months of age.  It selectively inhibits the activity of the enzyme JAK with activity against JAK1-dependent and JAK3-dependent cytokines (chemical mediators). It has both antipruritic and anti-inflammatory properties by reducing levels of pro-inflammatory cytokines such as interleukin (IL)-2, IL-4, IL-6, and IL-13, as well as inhibiting activity of IL-31, an enzyme involved in the development of pruritus and atopic dermatitis. Oclacitinib has also been used extra-label in cats. Adverse effects are uncommon, include vomiting and diarrhea, and generally resolve over time. As with any immunosuppressive drug, there may be an increased risk of infection or neoplasia development in treated animals.

cyclosporine (Atopica

an immunosuppressant approved for the treatment of atopic dermatitis in dogs and cats. It is initially given orally daily for so days in dogs and up to 6 Weeks in cats, after which dosing frequency may be reduced to the minimum required to maintain effectiveness (typically every two to four days). Cyclosporine should be administered on food or just after a meal in cats, but it should be given at least an hour before or two hours after eating in dogs. The most common adverse effects include vomiting and diarrhea that occur within the first few weeks of administration and are generally transient. As with any immunosuppressive drug, there may be an increased risk of infection or neoplasia developing in treated animals; therefore, bacteria and fungal infections should be treated before using cyclosporine, and it should not be used in cat with feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV).

Propionibacterium acnes injection (Immunoregulin, Eqstim

a USDA-labeled immunostimulant biologic used to treat Staphylococcus pyodermas and viral papillomatosis in dogs, FeLV and feline herpesvirus 1 (FHV-1) in cats, and respiratory infections in horses  It is a nonspecific immunostimulant that may induce macrophage activation, increase natural killer cell activity, and enhance cell-mediated immunity. It is an injectable preparation administered as an N, IP. or IM injection given more frequently in the first few weeks (frequency varies with the species) and gradually given less frequently over time. Adverse effects include pain at the injection site if given intramuscularly, postinfection lethargy, fever, chills, and anorexia, and rare anaphylactic reactions. It is stored refrigerated and shaken before using.

Seborrhea

also called seborrheic dermatitis, is a skin condition characterized by abnormal flaking and scaling of the outermost layer of the epidermis. Seborrhea accompanied by increased production of sebum (oil) is seborrhea oleosa. Seborrhea without increased production of sebum is seborrhea sicca. Products used to treat seborrhea are called antisebonbeic drugs. One important group of antisebormelc drugs is the keratolytics, which remove excess keratin and promote loosening the outer layers of the epidermis. Keratolytics break down the protein structure of the keratin layer, permitting easier removal of this compacted material. Keratolytics are found in medicated shampoos to help in the treatment of seborrhea.

sulfur

is keratolytic, antipruritic, antibacterial, antifungal, and antiparasitic. slows down epidermal cell proliferation and tends to be nonirritating and nonstaining to the animal. used to treat seborrhea sicca. It is not a good degreasing agent and is not as drying as other antiseborrheic agents. Products include KeraSeb Shampoo, Exfolux Shampoo, and Sulfur Benz Shampoo.

salicylic acid

is keratolytic, antipruritic, and antibacterial. Salicylic acid lowers skin pH resulting in increased hydration of keratinocytes and is used to treat seborrhea sicca and hyperkeratotic skin disorders. Products include Gentleseb Shampoo, Sebolux Shampoo, Derma-Clens Cream, and Solva-Ker Gel

coal tar

is keratolytic and degreasing. suppresses epidermal growth and DNA synthesis. It is irritating and may stain light-colored haircoats. used to treat seborrhea oleosa and may be irritating in cats. Products include Nova Pearls Medicated Coal Tar Shampoo, Sulfodene Medicated Shampoo and Conditioner, and ImrexTar and Sulfur Shampoo

benzoyl peroxide

is keratolytic, antipruritic, antibacterial, and degreasing. It lowers skin pH and disrupts microbial cell membranes. It is used to treat seborrhea dermatitis in which overproduction of oil occurs and also for moist dermatitis (hot spots), pyoderma, stud tail, and a variety of skin lesions that are moist and/or are contaminated with bacteria. Products include BPO-3 Shampoo, Benzoyl Plus Shampoo, and Peroxiderm Shampoo

selenium sulfide

is keratolytic, degreasing, and antifungal. It interferes with hydrogen bond formation in keratin and is used to treat seborrhea and eczema. Use of selenium sulfide may result in irritation, and it is available in human shampoo products. . essential fatty acids, which affect arachidonic acid levels in lipids in the cell membrane, have antipruritic and anti-inflammatory properties. Essential fatty acids can improve coat quality, relieve dry skin, and improve keratinization in addition to controlling itching and inflammation. Products include DermaLyte Shampoo, Hylagroom Shampoo, and Hylagroom Mouse

 phytosphingosine

is a ceramide (waxy material meant to mimic the normal lipid, composition of the epidermis). Ceramides are part of the intracellular cement of skin cells and are key molecules in the natural defense of skin. Phytosphingosine helps maintain moisture balance in the skin, which helps control dry, scaly skin. It may also have anti-inflammatory and antimicrobial properties. Products include DOUXO Calm Shampoo, DOUXO Seborrhea Spot On, and DOUXO Calm Gel

astringent

agent that constrict tissues. stop discharge by precipitating protein, have some antibacterial properties, used to treat moist dermatitis (hot spots) and other moist skin lesions. Ex. combination product that contains salicyclic aicd, tannic acid, and boric acid (stanisol). Isopropyl alcohol serves as an astringent when present in a variety of products

acetic acid

substances that kill or inhibit the growth of microorganisms on living tissue. acetic acid is effective against Pseudomonas sp. Ex. (usually found in ear preparations). Combination skin products that include acetic acid, chlorhexidine, and ketoconazole (HexaChlor-K spray, MalAcetic, Mel A Ket).

Alcohol

bactericidal, astringent, and cooling. Used to clean skin (70%) and to treat musculoskeletal pain by increasing blood flow to the area (90%). 50% to 70% (for cleaning or as solvent) 90% for musculoskeletal pain).

Benzalkonium Chloride

antibacterial and antifungal. used to treat ringworm and other fungal infections. Benzalkonium chloride is found in Dermacide.

Chlorhexidine

bactericidal, fungicidal, and partially virucidal. the solution has a 24 h residual effect. As a sole agent is in products including Nolvasan solution, Scrub, and Ointment. Chlorhex, TrizChlor.

Chloroxylenol

disrupts bacterial cytoplasmic membranes. Effective against bacterial, fungi, and viruses. Used as a presurgical skin preparation, wound cleaner, and to treat skin infections. as a sole agent in surgical scrubs and handwashes. Can be found in combination products with Ketoconazole (Pharmaseb Flush, Shampoo, and Spray) with miconazole nitrate (vet solutions sebazole shampoo), and salicylic acid and sodium thiosulfate (universal Medicated shampoo)

Enzymes

effective against bacteria, fungi, and viruses. May be used alone or in combination with products that control itching. May be found in oral products such as dental sticks to prevent plaque. Lactoperoxidase, lysozyme, and lactoferrin combination products include Zymox spray and cream. may be combined with hydrocortisone, hydrogen peroxide and or iodine

Hypochlorous acid

has antibacterial, antifungal, and antiviral properties. used to treat wounds, burns, incision sites, and to accelerate healing. as a sole agent is found in Veterincyn products and Biovetrex skin and wound cleanser.

Iodine

bactericidal, fungicidal, virucidal, and sporicidal (as a 1% solution). used as a presurgical skin preparation, wound cleaner, and to treat skin infections. Found in Betadine solution and scrub, tincture of Iodine, Lugol’s solution and Xenodine spray.

Povidone

Liberates free iodine and is preferred over iodine solution or tincture (containing alcohol) because it is less irritating to skin

Propylene Glycol

antibacterial and antifungal. used typically as solvents or vehicles for other drugs (goes by generic name).

Triclosan

antibacterial for both Gram negative and Gram positive bacteria. Treats superficial pyodermas. sole agents include Equine America Fungazol shampoo and Triclosan SHampoo

Aluminum acetate (burow’s solution)

soak that is drying and mildly antiseptic. used to relieve itching and inflammatory discharge. found in Cort/Astrin solution, Hydro-B 1020, Domeboro powder and tablets

Magnesium Sulfate

used in wound dressings to draw fluid out of tissue. found in Epson Salts.

Caustics

substances that destroy tissue. used to treat warts and excessive granulation tissue (proud flesh in horses) ex. silver nitrate, Equine Hoofpro, copper suspension, copper sulfate pentahydrate

counterirritants

substances that produce irritating and inflammation in areas of chronic inflammation. thought to increase blood supply to the area, which in turn brings wbc, antibodies to the area to stimulate healing and carries away kinins to relieve pain. Lin O Gel (alcohol, camphor, menthol, and iodine). Scarlet Oil Pump spray (camphor, menthol, phenol, scarlet red, pine oil, and eucalyptus oil)

immunomodulators

substances that have an effect on the immune system (either immunostimulatory or immunosuppressive.

• Imiiquimod (Aldara) stimulates patients monocytes and macrophages to induce regression of viral protein production. used to treat sarcoid in horses, squamous cell carcinoma, feline herpes viral dermatitis, and localized solar dermatitis.

• Tacrolimus (Protopic) inhibits T lymphocyte activation. used to treat atopic dermatitis, discoid lupus erythematosus, pemphigus, and perianal fistulas.

• Pimecrolimus (Elidel) inhibits T lymphocyte activation. used to treat atopic dermatitis discoid lupus erythematosus, pemphigus, and perianal fistulas

Tretinoin (Retin A)

retinoid substance that stimulate cellular mitotic activity, increases cell turnover, and decreases the cohesiveness of follicular epithelial cells. used to treat chin acne, callous pyoderma, and footpad hyperkeratosis

Hairy Heel Warts

microbial infection of the soft tissues surrounding the hooves. Papillomatous (digital dermatitis. occurs mainly in dairy cows and produce inflamed, red lesions on the skin of the hoof, usually just behind the interdigital cleft. believed to be caused by bacteria of the Treponema genus, a spirochete that thrives in muddy, dirty, and wet conditions. Treated topically with antibiotics or other drugs using a footbath, spray or application of a liquid, paste or powder under a bandage. traditional footbaths are the least effective because of the limited contact time. They are better for routine control. Tetracycline, lincomycin, chlorine bleach, salicylic acid and zinc sulfate have been used as treatment. Copper sulfate and formalin have been used but copper sulfate might contaminate the soil and formalin is a carcinogen. Lincomycin is toxic to rumen microbes.

Foot rot

caused by Fusobacterium necrophorum and Porphyromas levii. anaerobic bacteria that are part of normal GI flora of cattle. more common during wet periods like midwinter and early summer. it begins when the skin between the claws of the hoof become damaged. may have foul smelling discharge and redness of soft tissue. Use mineral supplementation of zinc or iodine has been used

thrush

caused by Spherophorus neaophorus, it invades the grooves of the frog and it destroys tissue, a black discharge is observed in the frog followed by inflammation and lameness.

proud flesh

prevents the wound from forming epithelial tissue and can become so large that it destroys the original wound. It occurs most commonly on the distal limbs due the constant movement of the horse's leg that impairs healing. The risk of proud flesh developing can be reduced through good wound management including bandaging with a nonstick pad and conforming gauze bandage to prevent wound contamination and reduce motion of tissue. The addition of an elastic bandage can apply pressure to prevent granulation tissue from becoming exuberant. If proud flesh forms, its treatment varies depending on the extent of overgrowth. Applying topical glucocorticoid drugs directly to the granulation tissue can inhibit the growth of exuberant tissue, and then bandaging the area can encourage epithelialization of the wound. Surgical removal of moderate to severe overgrowth of granulation tissue may be needed and can be performed with the horse standing. Extremely large amounts of granulation tissue need to be removed under general anesthesia or in several stages due to the amount of blood that can be lost. Following surgery, a splint or cast should be applied to prevent granulation tissue regrowth. Caustic agents such as copper sulfate have been used in the past to treat proud flesh, but they can inhibit the regrowth of healthy tissue as well as undesirable excess granulation tissue.

Sarcoids

the most common skin tumor of horses, are commonly seen at sites of previous injury in the genital region, ventral thorax, abdomen, and head. Sarcoids are nonmalignant tumors but become problematic because they enlarge, spread, and/or multiply locally and can cause irritation and bleed if rubbed. Sarcoids are believed to be caused by the bovine papilloma virus; however, there may also be a genetic predisposition in particular breeds and bloodlines. The virus may be spread by flies, by management practices such as sharing contaminated tack, or from contaminated pasture. Sarcoids can be diagnosed via biopsy; however, taking the biopsy risks uncontrollable expansion of the lesion. Treatment of sarcoids includes cryotherapy, surgical removal (which may spread the tumor), local immunostimulating drugs such as the Bacillus Calmette-Gurein (BCG) vaccine and Propionibacterium acnes injection, and acyclovir

Nonsteroidal topical antipruritic drugs

topical anesthetics: lidocaine (Hexa-Caine, Dermacool Spray with Lidocaine, BioCalm)· lidocaine with prilocaine cream (EMLA) tetracaine (TetCaine) pramoxine (Pramoxine Anti-Itch Shampoo, Pramoderm HC Spray Ipramoxine with hydrocortisone] and BenasootheShampoo and Conditions [pramoxine with oatmeal])

topical soothing agents: · oatmeal (Epi-Soothe and DermAllay Oatmeal Shampoo)

topical antihistamines: diphenhydramine (Atopicream [only contains diphenhydramine] and BenasootheShampoo and Conditioner [which contains diphenhydramine and pramoxine])

Triamcinolone

animax. intermediate glucocorticoid used to treat pruritus. topical antibiotic spray

retinoids

substances that stimulate cellular mitotic activity, increase cell turnover, and decrease the cohesiveness of follicular epithelial cells. ex. tretinoin used to treat skin acne, callous pyoderma, and footpad hyperkeratosis (Retin A)