Skin: allergic contact dermatitis

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Sections available in full article Introduction, Presenting signs, Age predisposition, Cost considerations, Pathogenesis, Etiology, Pathophysiology, Timecourse (incubation, duration), Diagnosis, Presenting problems, Client history, Clinical signs, Diagnostic investigation, Confirmation of diagnosis, Differential diagnosis, Treatment, Standard treatment, Monitoring, Prevention, Control, Sequelae, Prognosis, Expected response to treatment, Reasons for treatment failure, Sources, Publications, Vetstream contributor(s),
Contributors Mr David Scarff BVetMed CertSAD MRCVS
Dr Rosanna Marsella DVM DipACVD
Synonyms Contact hypersensitivity

Introduction

  • Rare, delayed or cell-mediated hypersensitivity reaction to contacted allergens in sensitized individuals.
  • Cause : various allergens.
  • Signs : alopecia, erythema, papular eruption.
  • Diagnosis : history, clinical signs (resolution with avoidance/confinement), histopathology, patch test.
  • Treatment : glucocorticoids, bathing, and removal of allergen.
  • Prognosis : good if allergen identified.

Diagnosis

Clinical signs

  • Alopecia and erythema of hairless or sparsely haired areas only.
  • Primary lesions are maculopapular eruptions.
  • Secondary lesions are hyperpigmentation and lichenification.
  • Secondary staphylococcal pyoderma Allergic contact dermatitis: neck.
  • Secondary seborrhea.
  • Ventral abdomen affected.
  • Ventral interdigital areas affected (not pads) Allergic contact dermatitis: paw.
  • Muzzle affected by plastic food dish dermatitis Allergic contact dermatitis.
  • Otitis externa due to ear preparations, eg neomycin-containing ointments Otitis externa: acute - erythema and edema.
  • Generalized disease with shampoo allergies.
  • Malasseziadermatitis Skin: malassezia disease.

Diagnosis

Differential diagnosis


Other pruritic skin diseases
  • Atopy Skin: atopy.
  • Flea allergy dermatitis Skin: flea bite hypersensitivity.
  • Food sensitivity Skin: food hypersensitivity.
  • Irritant contact dermatitis Skin: irritant contact dermatitis.
  • Staphylococcal pyoderma Skin: bacterial skin disease - overview.
  • Sarcoptic mange Skin: sarcoptic mange.
  • Cheyletiellosis Skin: cheyletiellosis.
  • Harvest mite Skin: neotrombicula autumnalis infestation.
  • Lice Skin: pediculosis.
  • Insect hypersensitivity Skin: external parasite bite reaction.
  • Malasseziadermatitis Skin: malassezia disease.
  • Peloderadermatitis.
  • Hookworm dermatitis Ancylostoma caninum.

Sequelae

Prognosis

  • Good if allergen identified.

  • Animal may be predisposed to other hypersensitivities, eg atopy Skin: atopy.

Expected response to treatment

  • Signs subside over 2-3 weeks in cases where allergen identified and removed.

Reasons for treatment failure

  • Failure to identify offending allergen.
  • Inability to avoid recognized allergen.

Sources

Publications

Refereed papers

  • Marsella R et al(1997) Use of pentoxifylline in the treatment of allergic contact reactions to plants of the Commelinanceae family in dogs. Vet Derm 8 , 121-126.
  • Walder E J & Conry J D (1994) Contact dermatitis in dogs and cats - pathogenesis, histopathology, experimetal induction and case reports. Vet Derm 5 , 149-161.
  • Prelaud P, Heripret D & Atleer B A (1990) Allergic contact dermatitis in the dog - principles and diagnosis. Vet Clin North Am 20 , 1443-1456.
  • Kunkle G A (1988) Contact dermatitis. Vet Clin North Am 18 , 1061-1068.

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