Acral Lick Dermatitis

Basics

Overview

Chronic lesions directly caused by self-trauma.
A cycle of licking, pruritus, and secondary infection develops.

Systems Affected

Skin/Exocrine

Signalment

Dogs.
Most common in large breeds-especially Doberman pinschers, Labrador retrievers, Great Danes, Irish and English setters, golden retrievers, Akitas, Dalmatians, boxers, Shar-Peis, and Weimaraners.
Age at onset-varies (especially with cause).
No sex predilection.

Signs

Excessive licking of the affected area.
Alopecic, eroded, thickened, and raised firm plaques with scabs and exudation, usually located on the dorsal aspect of the carpus, metacarpus, tarsus, or metatarsus.
Lesions often occur singly or may be multiple.

Causes & Risk Factors

Focal trauma to the area initiating a lick-itch cycle.
Anything causing a local irritation or lesion may initiate response.
Associated diseases-staphylococcal furunculosis, hypersensitivity, endocrinopathy, demodicosis, dermatophytosis, foreign body reaction, neoplasia, underlying joint disease or arthritis, trauma, neuropathy, psychogenic, or sensory nerve dysfunction.

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

Neoplasia
Bacterial furunculosis
Focal demodicosis
Focal dermatophytosis

CBC/Biochemistry/Urinalysis

Normal except in cases of endocrinopathy.

Other Laboratory Tests

Endocrinopathy-free T₄/TSH; ACTH stimulation test or LDDST.

Imaging

Radiology-neoplasia; local trauma; radiopaque foreign bodies; bony proliferation may be seen secondary to the chronic irritation; evidence of underlying arthritis if over a joint.

Diagnostic Procedures

Skin scrapings-demodicosis.
Dermatophyte culture-fungal infection.
Epidermal cytology-bacterial infection.
Bacterial culture and sensitivity-tissue cultures may differ from surface culture.
Food-elimination diet-determine food allergy.
Intradermal allergy testing-atopy.
Biopsy-to rule out neoplasia, other infections.
Behavioral history.
Neurologic and orthopedic evaluation.

Pathologic Findings

Histopathology-epidermal hyperplasia, plasmacytic dermal inflammation, folliculitis, furunculosis, perihidradenitis, hidradenitis, and vertical streaking fibrosis.

Treatment ⬆ ⬇

Treatment

Behavioral therapy: attempt to identify psychological causes and remediate.
Physical restraints-Elizabethan collars and bandaging permit healing.
Therapeutic laser-one controlled study did not demonstrate efficacy.
Diet-no modification unless food hypersensitivity is suspected.
Difficult to treat, especially if no underlying cause is found; warn owner that patience and time are necessary.
Surgery (laser or standard)-may cause increased licking and attention to a larger affected area; if underlying causes are not addressed, recurrence is likely.

Medications ⬆ ⬇

Medications

Drug(s)

Antibiotics

Based on bacterial culture and sensitivity.
Administer until infection is completely resolved; often at least 6 weeks.

Systemic

Antihistamines-e.g., hydroxyzine (1–2 mg/kg PO q12h); chlorpheniramine (4–8 mg/dog PO q12h; maximum of 0.5 mg/kg q12h).
SSRIs: e.g., fluoxetine (1 mg/kg PO q24h); paroxetine (0.5–1 mg/kg PO q24h).
Dopamine antagonists: e.g., naltrexone (2.2 mg/kg PO q12–24h).
TCAs: e.g., amitriptyline (1.1–2.2 mg/kg PO q12h; doxepin (3–5 mg/kg PO q12h; maximum 150 mg q12h); clomipramine (1–3.5 mg/kg PO q12–24h).
Combine and/or withdraw administration of these medications carefully.

Topical

Flunixin meglumine and fluocinolone in dimethyl sulfoxide (combined).
Topical capsaicin products.
Intralesional corticosteroids rarely helpful.
Topical medications should be applied with gloves.
Animals should be kept from licking the area for 10–15 minutes.

Contraindications/Possible Interactions

Doxepin-caution using with monoamine oxidase inhibitors, clonidine, anticonvulsants, oral anticoagulants, steroid hormones, antihistamines, or aspirin.
Antihistamines-may cause sedation.
Psychotropic medications should be combined and/or withdrawn carefully.
Cardiotoxicity and hepatoxicity-rare cases in animals on TCAs. Routine monitoring recommended.

Follow-Up ⬆ ⬇

Follow-Up

Monitor level of licking and chewing closely.
Treat underlying disease to prevent recurrence.
If no underlying disease is detected, suspect psychogenic causes (compulsive or self-mutilation disorder); prognosis is guarded.

Miscellaneous ⬆

Miscellaneous

Age-Related Factors

Dogs <5 years old-strongly consider allergy

Zoonotic Potential

Transmitted to humans only if dermatophytosis is the underlying cause; exceedingly rare.
Methicillin resistant Staphylococcus aureus may have zoonotic implications.

Abbreviations

ACTH = adrenocorticotropin hormone
LDDST = low-dose dexamethasone suppression test
SSRI = selective serotonin reuptake inhibitor
TCA = tricyclic antidepressant
TSH = thyroid stimulating hormone

Author Alexander H. Werner

Consulting Editor Alexander H. Werner

Acknowledgment The author and editors acknowledge the prior contribution of Jean S. Greek.

Suggested Reading

Shumaker AK, Angus JC, et al. Microbiological and histopathological features of canine acral lick dermatitis. Vet Dermatol 2008, 19(5):288–298.

section name header

Basics ⬇

Diagnosis ⬆ ⬇

Treatment ⬆ ⬇

Medications ⬆ ⬇

Follow-Up ⬆ ⬇

Miscellaneous ⬆