Contact dermatitis

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Contact allergy in a Pit Bull due to hypersensitivity to wandering jew plant[1]

Contact allergy (contact dermatitis) is a relatively common dermatopathy of dogs characterized by dermatitis related to skin contact with various chemicals[2].

A wide range of chemical can elicit an eruptive, acute-onset cutaneous allergic inflammatory response which leads to wheal or erythema formation and consequential dermatitis.

These include plastic food bowls, industrial chemicals such as chromium metals[3], acids and alkalis, detergents, solvents, soaps, and petroleum byproducts, sap from certain weeds, trees, grasses (especially wandering jew (Tradescantia spp) and inch plant (Callisia fragrans))[4][5] and topical insecticidal collars, sprays, powders, foams, and shampoos[6].

Contact dermatitis may induce severe reactions in some dogs such as metaflumizone-amitraz incriminated in triggering secondary pemphigus foliaceus[7] and some shampoos inducing superficial necrolytic dermatitis[8].

Contact dermatitis often occurs in glabrous skin regions such as the abdomen and less commonly the feet, chin, nose and genitals. Irritant contact dermatitis can occur after a single exposure or repeated exposure.

Clinical symptoms are usually confined to the skin and include hypersensitivity-induced pruritus with secondary moisture-associated dermatitis, intertrigo and pyoderma[9]. In contact dermatitis associated with the feet, secondary pododermatitis is common.

The diagnosis of contact dermatitis is made by results of avoidance and/or provocation tests and/or patch tests[10].

A differential diagnosis in most dogs would include atopy, food allergy, parasites such as Demodex spp, Pelodera spp[11] and fleas.

Treatment is usually achieved by removal of dog from cause and treating with palliate topical glucocorticoids and antimicrobial if indicated.

References

  1. Pitbull chat
  2. White PD (1991) Contact dermatitis in the dog and cat. Semin Vet Med Surg (Small Anim) 6(4):303-315
  3. Kimura T (2007) Contact hypersensitivity to stainless steel cages (chromium metal) in hairless descendants of mexican hairless dogs. Environ Toxicol 22(2):176-184
  4. Lee SE & Mason KV (2006) Immediate hypersensitivity to leaf extracts of Callisia fragrans (inch plant) in a dog. Vet Dermatol 17(1):70-80
  5. Bauer CL et al (2010) Determination of irritant threshold concentrations to weeds, trees and grasses through serial dilutions in intradermal testing on healthy clinically nonallergic dogs. Vet Dermatol 21(2):192-197
  6. Turner V et al (2011) A survey for small animal veterinarians regarding flea and tick control pesticide products. Can Vet J 52(10):1080-1082
  7. Oberkirchner U et al (2011) Metaflumizone-amitraz (Promeris)-associated pustular acantholytic dermatitis in 22 dogs: evidence suggests contact drug-triggered pemphigus foliaceus. Vet Dermatol 22(5):436-448
  8. Murayama N et al (2008) A case of superficial suppurative necrolytic dermatitis of miniature schnauzers with identification of a causative agent using patch testing. Vet Dermatol 19(6):395-399
  9. Rosser EJ (1997) German shepherd dog pyoderma: a prospective study of 12 dogs. J Am Anim Hosp Assoc 33(4):355-363
  10. Trenti D et al (2011) Suspected contact scrotal dermatitis in the dog: a retrospective study of 13 cases (1987 to 2003). J Small Anim Pract 52(6):295-300
  11. Saari SA & Nikander SE (2006) Pelodera (syn. Rhabditis) strongyloides as a cause of dermatitis - a report of 11 dogs from Finland. Acta Vet Scand 48:18