ISSN 2398-2950      

Skin: allergic contact dermatitis

ffelis
Contributor(s):

Ian Mason

David Scarff

Synonym(s): Contact hypersensitivity


Introduction

  • Very rare, cell-mediated hypersensitivity reaction to contacted environmental allergens in ed individuals.
  • Contact reactions are more commonly due to irritant contact dermatitis Skin: irritant contact dermatitis than contact hypersensitivity.
  • Signs: pruritus, maculopapular dermatitis, usually affecting the sparsely haired skin in areas in contact with the allergen.
  • Diagnosis: elimination of allergen and subsequent provocative exposure, patch testing.
  • Treatment: prevention of access to offending allergens.
  • Prognosis: variable, may not be possible to identify and exclude allergen.

Pathogenesis

Etiology

  • Plant resins and oils.
  • Common medications, eg neomycin Neomycin in otic preparations.
  • Home furnishings (carpet mordants and dyes).
  • Cleaning products (detergents, polishes).
  • Chlorine in water.
  • Common flea collars (leather collars).
  • Insecticides.
  • Cat litter additives.
  • Plants (Commelinanceae family).

Predisposing factors

General

  • Topical application of medication or flea collar.
  • Site of skin.
  • Age of skin.
  • Degree of hydration.
  • Local environment of skin.

Specific

  • Overhydration of the corneum, eg occlusion or prolonged wetting.
  • pH (alkaline encourages penetration).
  • Lipophilicity (may be absorbed through the sebaceous gland or root sheath).
  • Ability to provoke inflammation (inflammation increases epidermal permeability).

Pathophysiology

  • Rare in the cat due to regular grooming and removal of foreign proteins. Also as hair coat over much of body.
  • In the dog, chemicals act as haptens to bind to proteins   →   a conjugate   →   binding to Langerhans cells in the skin   →   initiation of a T-cell response. Following exposure to antigen in a ed animal, mononuclear cells infiltrate the skin. These are removed by ed lymphocytes leaving intraepidermal vesicles. This type IV hypersensitivity reaction leads to pruritus (not yet proven in the cat).
  • An immediate hypersensitivity reaction may also be involved.
  • Low molecular weight haptens link epidermal proteins to form antigens. Antigen is trapped, processed and presented by Langerhans' cells. They produce cytokines which attract T-cells, leading to activation of keratinocytes to release proinflammatory cytokines. They also travel to local lymph nodes to amplify the immune response .

Timecourse

  • Sensitization takes a minimum of 3 weeks, more commonly >2 years.
  • After contact with an allergen, clinical signs will take 48 hours approximately to develop in a sensitized cat (a delayed allergic reaction).

Diagnosis

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Treatment

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Prevention

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Outcomes

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Marsella R, Kunkle G, Lewis D (1997) Use of pentoxifylline in the treatment of allergic contact reactions to plants of the commelinanceae family in dogs. Vet Derm (2), 121-126 Wiley Online Library.
  • Conroy J D (1983) An overview of immune-mediated mucocutaneous diseases of the dog and cat. I. Diseases based on allergic reactions. Am J Dermatopathol (5), 505-509 PubMed.
  • Austin V H (1979) Alopecias of the dog and cat. Part II. Mod Vet Pract 60 (2), 130-134 PubMed.
  • Scott D W (1978) Immunologic skin disorders in the dog and cat. Vet Clin North Am (4), 641-664 PubMed.

Can’t find what you’re looking for?

We have an ever growing content library on Vetlexicon so if you ever find we haven't covered something that you need please fill in the form below and let us know!

 
 
 
 

To show you are not a Bot please can you enter the number showing adjacent to this field

 Security code