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==Introduction==
==Introduction==
[[Image:Chronic Allergic Otitis.jpg|thumb|right|200px|Chronic allergic otitis in the dog. Source: Wikimedia Commons; Author: Caroldermoid (2006)]]
[[Image:Chronic Allergic Otitis.jpg|thumb|right|200px|Chronic allergic otitis in the dog. Source: Wikimedia Commons; Author: Caroldermoid (2006)]]
*Food allergy: ruled out by a dietary exclusion trial.
*Food allergy: ruled out by a dietary exclusion trial.
*[[Flea Allergic Dermatitis|Flea allergy dermatitis]]: ruled out observing response to ectoparasiticides.
*[[Flea Allergic Dermatitis|Flea allergy dermatitis]]: ruled out observing response to ectoparasiticides.
*Contact dermatitis: ruled out by confining animal to one area covered in e.g. newspaper.
*[[Contact Dermatitis|Contact dermatitis]]: ruled out by confining animal to one area covered in e.g. newspaper.
*[[Sarcoptic Mange|Scabies]]:ruled out observing response to ectoparasiticides.
*[[Sarcoptic Mange|Scabies]]:ruled out observing response to ectoparasiticides.
===Clinical Signs===
===Clinical Signs===
Signs are often, but not always, seasonal. Pruritus is the hallmark of atopic dermatitis and may be the only complaint. This gives rise to self-trauma, causing lesions. Lesions commonly include alopecia, erythema, scaling, crusting, excoriations and salivary staining. Macular-papular eruptions are occasionally seen<sup>2</sup>. With time, lichenification, and hyperpigmentation develops. Because the route of allergen contact is thought to be percutaneous absorption<sup>1, 2</sup>, it follows that hairless regions are most frequently affected: the face, ears, axillae, feet and inguinal regions are predilection sites. Secondary infections such as superficial staphylococcal pyoderma and [[Malassezia pachydermidis|''Malassezia'']] are common, and otitis externa often occurs concurrently<sup>2, 3, 4</sup>. A small number of cases exhibit only chronic or recurrent otitis externa. Another uncommon presentation is allergic rhinitis, manifesting as sneezing, nasal discharge or allergic conjunctivitis<sup>1, 2</sup>.
Signs are often, but not always, seasonal. Pruritus is the hallmark of atopic dermatitis and may be the only complaint. This gives rise to self-trauma, causing lesions. Lesions commonly include alopecia, erythema, scaling, crusting, excoriations and salivary staining. Macular-papular eruptions are occasionally seen<sup>2</sup>. With time, lichenification, and hyperpigmentation develops. Because the route of allergen contact is thought to be percutaneous absorption<sup>1, 2</sup>, it follows that hairless regions are most frequently affected: the face, ears, axillae, feet and inguinal regions are predilection sites. Secondary infections such as superficial staphylococcal pyoderma and [[Malassezia pachydermidis|''Malassezia'']] are common, and otitis externa often occurs concurrently<sup>2, 3, 4</sup>. A small number of cases exhibit only chronic or recurrent otitis externa. Another uncommon presentation is allergic rhinitis, manifesting as sneezing, nasal discharge or allergic conjunctivitis<sup>1, 2</sup>.
Signs commonly seen in different species are:
:Dogs - face rubbing and foot licking; secondary [[Pyoderma|pyoderma]] or [[Seborrhea|seborrhea]]
:Cats - facial, ear or generalised pruritus, [[Feline Miliary Dermatitis|miliary dermatitis]], [[Feline Eosinophilic Granuloma|eosinophilic granuloma complex]], symmetric alopecia
:Horses - pruritic hea, pinnae, ventrum, legs, tailhead or recurrent [[Urticaria|urticaria]]
===Laboratory Tests===
===Laboratory Tests===
===Pathology===
===Pathology===
Gross findings reflect the lesions seen in life.
Gross findings reflect the lesions seen in life and lesions are generally due to self-trauma.
Histological changes are non-specific but include acanthosis, a mixed mononuclear perivascular dermatitis, sebaceous gland metaplasia and secondary superficial pyoderma<sup>1</sup>.
Histological changes are non-specific but include acanthosis, a mixed mononuclear perivascular dermatitis, sebaceous gland metaplasia and secondary superficial pyoderma<sup>1</sup>.
Other microscopical findings include: hyperplastic superficial perivascular dermatitis, mast cells, eosinophils and nonmetachromatic mononuclear cells. Perivascular inflammation may be involved especially in horses.
==Treatment==
==Treatment==
If left untreated, the degree of pruritus worsens, but atopic dermatitis is not life threatening unless intractable pruritus warrants euthanasia<sup>1</sup>. Some cases may spontaneously resolve.
If left untreated, the degree of pruritus worsens, but atopic dermatitis is not life threatening unless intractable pruritus warrants euthanasia<sup>1</sup>. Some cases may spontaneously resolve.
==Literature Search==
{{Learning
[[File:CABI logo.jpg|left|90px]]
|Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis00214.asp Atopy]<br>[https://www.vetstream.com/canis/Content/Illustration/ill02158.asp Atopy: acute on chronic]<br>[https://www.vetstream.com/canis/Content/Illustration/ill02166.asp ears]<br>[https://www.vetstream.com/canis/Content/Illustration/ill02164.asp Atopy: extremities]<br>[https://www.vetstream.com/canis/Content/Illustration/ill02165.asp Atopy: peri-orbital]
|literature search = [http://www.cabdirect.org/search.html?q=title:(%22Atopic+Dermatitis%22) Atopic Dermatitis publications]
<br><br><br>
[http://www.cabdirect.org/search.html?q=title:(%22Atopic+Dermatitis%22) Atopic Dermatitis publications]
[http://www.cabdirect.org/search.html?q=title:(%22Atopic+Dermatitis%22)+AND+od:(dogs) Atopic Dermatitis in dogs publications]
[http://www.cabdirect.org/search.html?q=title:(%22Atopic+Dermatitis%22)+AND+od:(dogs) Atopic Dermatitis in dogs publications]
[http://www.cabdirect.org/search.html?q=title:(%22Atopic+Dermatitis%22)+AND+od:(cats) Atopic Dermatitis in cats publications]
[http://www.cabdirect.org/search.html?q=title:(%22Atopic+Dermatitis%22)+AND+od:(cats) Atopic Dermatitis in cats publications]
}}
==Links==
==Links==
#Merck & Co (2008) '''The Merck Veterianry Manual (Eight Edition)''', ''Merial''.
#Merck & Co (2008) '''The Merck Veterianry Manual (Eight Edition)''', ''Merial''.
{{review}}
{{OpenPages}}
[[Category:Allergic Skin Diseases]]
[[Category:Allergic Skin Diseases]]
[[Category:Dermatological Diseases - Dog]] [[Category:Cat]]
[[Category:Dermatological Diseases - Dog]][[Category:Immunological Diseases - Dog]] [[Category:Dermatological Diseases - Cat]][[Category:Immunological Diseases - Cat]]
[[Category:Expert Review]]
[[Category:Type I Hypersensitivity Diseases]]
[[Category:Integumentary System - Hypersensitivity Reactions]]