Hot Spot - AKA Moist Eczema
Hot Spots and moist eczema are common names for
pyotraumatic dermatitis. Pyotraumatic dermatitis is a rapidly developing
surface bacterial skin infection secondary to self-induced trauma due to pain or
pruritis. Pruritis may be defined as the sensation that elicits the desire
to scratch. In animals prurities manfests as self-induced trauma due to
licking, chewing, rubbing, hair removal and irritability, and may even involve
personality changes. The skin functions as an "external nervous system".
It contains free nerve endings responsible for continuously relaying sensory
inputs, relating to touch, temperature, pain and pruritis to the brain or
central nervous system. Pruritis initiates a scratching response, however
the mechanisms by which scratching alleviates itching are still unknown.
The majority of pyotraumatic dermatitis cases are
complications of flea bit hypersensitivity. Other underlying causes may
include allergic skin diseases due to food hypersensitivities or
hypersensitivity to environmental factors (atopy), other ectoparasites (e.g.
sarcoptic mange or Chevletiella mites commonly known as walking dandruff), anal
sac problems, inflammations such as otitis externa (infection of the skin
covering the outer ear canal that leads into the ear drum), foreign bodies in
the coat, irritant substances which comes in contact with the animal's skin,
dirty unkempt coats, phychoses including anxiety, boredom, separation and
obsessive compulsive disorder, and painful musculoskeletal disorders.
It is usually a seasonal problem, being more common when
the weather is hot and humid. It commonly occurs in dogs, especially
thick-coated, long-haired breeds, but it rarely occurs in cats.
Lesions are usually single but may also be mulitple.
Lesions are often painful, and they are often located in close proximity to the
primary painful process. Lesions most frequently occur on the trunk, tail
base, outer thighs, neck or face. Lesions are acutely pruritic (having a
sudden onset) and the area of reddened (erythema), weeping and eroded skin with
accompanied hair loss (alopecia) and well demarcated margins enlarges rapidly.
A diagnosis of pyotraumatic dermatitis is usually based on
a history of sudden or acute onset, the physical appearance of the lesions, and
some association with a primary cause. A skin imprint on a glass slide
when studied under a microscope will reveal inflammatory cells and mixed
Treatment involves the identification and treatment of
underlying cause. Sedation or anaesthesia may be needed to thoroughly clip
and clean the affected area with povidone-iodine or chlorhexidene. Where
clipping is not possible in show dogs, an antiseptic shampoo should be used on
the unclipped affected areas. The nature of additional treatments will
depend on the severity of the lesion and the patient. If the pruritis is
mild, topical therapy is indicated and it involves the application of a cream or
a solution containing an antibacterial agent and a corticosteroid 2 - 3 times a
day for 5 to 14 days. If the pruritis is severe, topical as well as
systemic therapy is indicated. Systemic therapy includes antibiotic and
corticosteroid tablets or injections. To prevent further self-induced
trauma, the application of an Elizabethian collar may be indicated.
Therapy is effective if it is applied promptly and
vigorously, and the prognosis is good if the underlying cause can be corrected
Veterinary articles supplied by Dr S Strydom and published
with kind permission of DIA Publishing - publishers of KUSA Dogs in Africa
Dr Sunelle Strydom qualified as a veterinarian in 2004 at the Faculty of
Veterinary Science, University of Pretoria. She has a passion for writing and
the sharing of knowledge to promote animal health and welfare. She has written
several articles for KUSA Dogs in Africa as well as for Vra vir Faffa on the
Landbouweekblad website at www.landbou.com
Other articles which may be of interest:
Tick Bite Fever
Dog Health Conditions
Return from Hot Spots
- Ettinger S J and Feldman E C. 2000. Textbook of
Veterinary Internal Medicine 5th Edition. W.B. Saunders, USA
- Hill P B. 2002. Small Animal Dermatology.
Elsevier Science Ltd. London
- Medleau L and Hnilica K A 2001. Small Animal
Dermatology. A colour atlas and Therapeutic Guide. W.B. Saunders
- Scott D W, Miller W H and Griffen C E 2001.
Small Animal Dermatology 6th Edition. W.B. Saunders Company, USA
- MedicineNet.com (website). Available from
http://www.medterms.com on 28 October 2008.
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