Acute moist dermatitis, also known as hot spots, are localized, moist, reddened bacterial infections of the skin. A hot spot starts because something irritates the skin. The body’s response is either to itch or become inflamed. The itching then causes the dog to lick or chew the area, which further damages the skin, and creates a cycle of itching, scratching and chewing.

Hot spots can be caused by anything that irritates the skin and initiates an itch-scratch cycle, but the most common irritants are fleas. Other causes are allergies (flea, inhalant, food), parasitic disease (sarcoptic and demodectic mange), anal gland disease, poor grooming, tick and mosquito bites, burrs, and summer heat. They are most common in long-haired and heavy-coated breeds, and are more prevalent during the summer months. Typical locations for "hot spots" are the side of the face and the flank areas. Golden retrievers, Saint Bernards and young dogs seem to be predisposed to acute moist dermatitis.

WHAT TO WATCH FOR

Typically, your pet will exhibit the following:

Areas of hair loss with very red skin that is moist and oozing
In some cases, the skin becomes crusty or scabbed
Intense scratching. Hot spots are extremely itchy and your dog will scratch without letup

Diagnostic tests are needed to recognize acute moist dermatitis and exclude other diseases. However, your veterinarian can usually make a preliminary diagnosis based on a history of rapid onset and the clinical appearance of the lesions.

Treatment for acute moist dermatitis may include one or more of the following:

Clipping and cleaning of the affected areas. Lesions often are more extensive than they initially appear. Clipping the hair in the area is important to allow proper cleaning of the affected skin. Antibacterial solutions (chlorhexidine) or drying solutions (Burrow’s solution) combat infection and decrease pruritus (itchiness).

Interruption of the pruritic cycle. This is crucial to successful treatment. Once the cycle has been triggered, it is important to stop it so as to prevent self-mutilation. Orally-administered cortisone-like drugs often are used for a short period of time to make the dog more comfortable. Your dog may be more hungry and thirsty while receiving corticosteroids – this is a common side effect of this medication. As a consequence, the dog may need to urinate more frequently than normal. Some dogs may also pant as a consequence of corticosteroid therapy.

Secondary bacterial infection must be treated when present. In some cases, damage is so extensive that bacteria proliferate, resulting in secondary infection. In such instances, an antibiotic may be prescribed for 2 to 3 weeks.

Identification and treatment of the underlying cause is important to prevent recurrent episodes of acute moist dermatitis. Most cases are secondary to flea allergy and aggressive flea control usually is necessary.

Clean the affected areas with antibacterial and astringent products daily until healing is complete. Make sure that your dog has sufficient water while receiving corticosteroids. House soiling incidents may occur during corticosteroid therapy if the dog is not allowed outdoors frequently enough.

If your dog has flea allergy and is prone to develop hot spots, you should be aggressive with your flea control program. In addition to treating the environment, you also should apply an appropriate insecticide or repellent to your dog to prevent flea bites.

INFORMATION IN-DEPTH

Hot spots (also called acute moist dermatitis or pyotraumatic dermatitis) are localized, moist, reddened areas on the skin caused by self-mutilation. Acute moist dermatitis is a very common skin disease of dogs. hot spots are frequently seen in long-haired and heavy-coated breeds, and are more prevalent during the summer months.

The precise sequence of events leading to acute moist dermatitis is not known but anything that can initiate an itch-scratch cycle can lead to acute moist dermatitis. Common underlying causes of hot spots include allergies (flea allergy, atopy, food allergy), parasitic diseases (sarcoptic and demodectic mange), anal gland disease, clipping and grooming. Less common causes of hot spots include ringworm (dermatophytosis), drug reactions, autoimmune disease in which the body fails to identify self-components and reacts against normal tissues, and vasculitis (inflammation of blood vessels).

Clinically, the lesions of acute moist dermatitis are secondary to self-inflicted trauma. Strangely, even severe self-trauma in some dogs will not create a hot spot while in others minimal self trauma may do so. The role of bacteria in the development of hot spots also is not clear. Some cases of acute moist dermatitis seem to be initiated by folliculitis (i.e. inflammation and infection of hair follicles), and this seems to be common in Saint Bernards and Golden retrievers. Other affected dogs do not seem to have an important bacterial component and respond to clipping of the hair, cleansing of the skin and corticosteroid therapy.

RELATED SYMPTOMS OR AILMENTS

The lesions of acute moist dermatitis are reddened (erythematous), swollen, and hairless. They exude a serous discharge and are painful. Their onset and progression are rapid. Pruritus (itchiness) is intense, and severe self-trauma can cause severe lesions in a very short period of time.

Two types of acute moist dermatitis occur. One type does not have an important bacterial component and manifests as a superficial ulcerated plaque. The second type, in addition to being an ulcerated plaque, also has peripheral papules (small reddened bumps) suggestive of bacterial folliculitis. Typical locations of hot spots are the hindquarters and the sides of the face below the ear. Lesions on the hindquarters usually are caused by underlying flea allergy, whereas those on the side of the face usually are associated with concurrent ear inflammation (otitis) secondary to allergies.

VETERINARY CARE IN-DEPTH

DIAGNOSIS IN-DEPTH

Diagnosis is based on history and clinical signs. It is important to rule out demodectic or sarcoptic mange as a possible underlying cause of acute moist dermatitis. Thus, microscopic examination of several deep skin scrapings should be performed.

Microscopic examination of smears from the exudate is useful to identify a bacterial component. If bacterial infection (pyoderma) is present, degenerate neutrophils (a type of white blood cell) with bacteria (usually Staphylococci) inside of them often are found.

If the animal has a long history of acute moist dermatitis, it is important to identify the underlying disease. A diagnostic evaluation for flea allergy and other allergies (an elimination food trial) should be performed.

Identification of the underlying cause of the pruritus (itchiness) is an important part of treatment to prevent recurrence. The involved area should be clipped and gently cleansed with a mild antiseptic. Products containing benzoylperoxide are used to wash the area. Astringent products (Burrow's solution) can be used for the first few days to dry out the area. Antipruritic sprays containing hydrocortisone, lidocaine or pramoxine also are helpful but short-acting.

Cortisone-like drugs are often prescribed for a short period of time. Elizabethan collars may be used to prevent self-trauma. These collars are made of large sheets of plastic material that encircle the pet's neck and prevent them from licking or biting their skin.

Antibiotic therapy for a minimum of three weeks may be necessary in animals with secondary bacterial folliculitis.

Long-term injectable corticosteroids should be avoided in the management of hot spots.