Lick granuloma is a form of self-trauma and skin disorder in which most commonly dogs, but also cats, continuously lick a small area of their body until it becomes raw and inflamed. The most common areas affected are the lower (distal) portions of their legs, such as the carpus (wrist), or sometimes another part of their body such as the base of their tail.

The lesion can initially be red, shiny, swollen, hairless, irritated, and bleeding, similar to a hot spot (wet eczema). Eventually a raised hard plaque forms.

A lick granuloma, also known as acral lick dermatitis, is a skin disorder found most commonly in dogs, but also in cats. In dogs, it results typically from the dog's urge to lick the lower portion of one of his or her legs.

The lesion can initially be red, swollen, irritated, and bleeding, similar to a hot spot (wet eczema). The animal's incessant licking of the lesion eventually results in a thickened, firm, oval plaque, which is the granuloma.

A major cause of lick granuloma appears to be psychological, related to stress, anxiety, separation anxiety, boredom, or compulsiveness. Lick granulomas are especially seen in active dogs left alone for long periods of time. One theory is that excessive licking causes endorphin release, which reduces pain and makes the animal feel euphoric temporarily; that effect then causes an addiction to licking.

Other triggers include itchy skin, painful conditions caused by trauma to the skin, arthritis, neuralgia, and peripheral neuropathy. A bacterial or fungal infection of the skin can also trigger itching, as can skin mites, allergies, a reaction to an environmental irritant or toxin, hyperthyroidism, and certain types of cancer.

Treatment of the primary cause, if known, is essential. In psychogenic cases, psychological factors should be identified and addressed, such as being left alone all day, being confined, and changes in the household.

Redness around the lips in circumoral distribution with dryness and scale is typical. Chapping may also occur, especially in cold weather.

Repeated licking resulting in a cycle of wetting and drying causes the redness, fissuring and scale. IIt can also occur with lip chewing, thumb sucking or excessive drooling.

Wind instrument players may also experience lip licker's dermatitis.

Compulsive licking of lips causing lick lip dermatitis is also seen as psychological disorder.

Persistent and continuous breathing from the mouth can cause dry lips and result in temptation to repeated lick lips.

The intense contact between a musical instrument and skin may exaggerate existing skin conditions or cause new skin skin conditions. Skin conditions like hyperhidrosis, lichen planus, psoriasis, eczema, and urticaria may be caused in instrumental musicians due to occupational exposure and stress. Allergic contact dermatitis and irritant contact dermatitis are the most common skin conditions seen in string musicians.

Pityriasis amiantacea (also known as "Tinea amiantacea") is an eczematous condition of the scalp in which thick tenaciously adherent scale infiltrates and surrounds the base of a group of scalp hairs. It does not result in scarring or alopecia.

Pityriasis amiantacea was first described by Alibert in 1832. Pityriasis amiantacea affects the scalp as shiny asbestos-like (amiantaceus) thick scales attached in layers to the hair shaft. The scales surround and bind down tufts of hair. The condition can be localised or covering over the entire scalp. Temporary alopecia and scarring alopecia may occur due to repeated removal of hairs attached to the scale. It is a rare disease with a female predilection.

Pityriasis amiantacea can easily be misdiagnosed due its close resemblance to other scalp diseases such as psoriasis, seborrhoeic dermatitis or lichen planus. However in pityriasis amiantacea the scales are attached to both the hair shaft and the scalp. Pityriasis amiantacea may be present with other inflammatory conditions such as atopic dermatitis or seborrhoeic dermatitis and sebaceous scales and alopecia can occur. According to the dermatology text Bolognia this condition is most often seen in psoriasis, but may also be seen in secondarily infected atopic dermatitis, seborrheic dermatitis, and tinea capitis.

Nummular dermatitis is characterized by chronic or relapsing itchy coin-sized ovoid-shaped red plaques. They can occur on the trunk, limbs, face, and hands.

Other rashes that occur in the diaper area include seborrhoeic dermatitis and atopic dermatitis. Both Seborrheic and Atopic dermatitis require individualized treatment; they are not the subject of this article.

- Seborrheic dermatitis, typified by oily, thick yellowish scales, is most commonly seen on the scalp (cradle cap) but can also appear in the inguinal folds.

- Atopic dermatitis, or eczema, is associated with allergic reaction, often hereditary. This class of rashes may appear anywhere on the body and is characterized by intense itchiness.

The diagnosis of IDD is made clinically, by observing the limitation of an erythematous eruption to the convex surfaces of the genital area and buttocks. If the diaper dermatitis occurs for greater than 3 days it may be colonized with "Candida albicans", giving it the beefy red, sharply marginated, appearance of diaper candidiasis.

A hot spot, or "acute moist dermatitis", is an acutely inflamed and infected area of skin irritation created and made worse by a dog licking and biting at itself. A hot spot can manifest and spread rapidly in a matter of hours as secondary Staphylococcus infection causes the top layers of the skin to break down and as pus becomes trapped in the hair. Hot spots can be treated with corticosteroid medications and oral as well as topical antibiotic application, as well as clipping hair from around the lesion. Underlying inciting causes include flea allergy dermatitis, ear disease or other allergic skin diseases. Dogs with thick undercoat are most subject to getting hot spots.

Frequent, chronic contact of instruments to skin may make it callous by the thickening of stratum corneum. Use of 'thumb position' in cellists may cause callosity of left thumb. Garrod's pads are seen on the dorsal left second and third fingers over the proximal interphalangeal joints in violinists. Drummer's digit is the callosity seen on the lateral phalynx of the left finger. Callosities need treatment only when they are excessive or symptomatic.

Lesions emerge as well-demarcated psoriasiform or hyperkeratotic patches and 36 plaques, with a central clearing and an elevated border. Pagetoid reticulosis is a very slow progressive variant of mycosis fungoides and is usually localized unlike the latter .

Erythroderma is generalized exfoliative dermatitis, which involves 90% or more of the patient's skin. The most common cause of erythroderma is exacerbation of an underlying skin disease, such as psoriasis, contact dermatitis, seborrheic dermatitis, lichen planus, pityriasis rubra pilaris or a drug reaction. Primary erythroderma is less frequent and is usually seen in cases of cutaneous T-cell lymphoma, in particular in Sézary's disease.

The most common causes of exfoliative dermatitis are best remembered by the mnemonic device ID-SCALP. The causes and their frequencies are as follows:

- Idiopathic - 30%

- Drug allergy - 28%

- Lymphoma and leukemia - 14%

- Atopic dermatitis - 10%

- Psoriasis - 8%

- Contact dermatitis - 3%

- Seborrheic dermatitis - 2%

Differential diagnosis in patients with erythroderma may be difficult.

Erythroderma (also known as "Exfoliative dermatitis," "Dermatitis exfoliativa") is an inflammatory skin disease with erythema and scaling that affects nearly the entire cutaneous surface.

In ICD-10, a distinction is made between "exfoliative dermatitis" at L26, and "erythroderma" at L53.9.

Skin disorders are among the most common health problems in dogs, and have many causes. The condition of a dog's skin and coat are also an important indicator of its general health. Skin disorders of dogs vary from acute, self-limiting problems to chronic or long-lasting problems requiring life-time treatment. Skin disorders may be primary or secondary (due to scratching, itch) in nature, making diagnosis complicated.

Periorbital dermatitis (also known as "periocular dermatitis") is a skin condition, a variant of perioral dermatitis, occurring on the lower eyelids and skin adjacent to the upper and lower eyelids.

The bacteria staphylococci are present in the majority of cases. Treatment with systemic antibiotics and coal tar shampoo can completely clear the condition when Staphylococcus aureus bacteria are found. Fungal infections such as tinea capitis are known to mimic the symptoms of the condition and can be cleared with antifungal treatment.

A stinging and burning sensation with rash is often felt and noticed, but itching is less common. Often the rash is steroid responsive, initially improving with application of topical steroid. The redness caused by perioral dermatitis has been associated with variable level of depression.

Initially, there may be small pinpoint papule either side of the nostrils. Multiple small (1-2mm) papules and pustules then occur around the mouth, nose and sometimes cheeks. The area of skin directly adjacent to the lips, also called the vermillion border, is spared and looks normal. There may be some mild background redness and occasional scale. These areas of skin are felt to be drier and therefore there is a tendency to moisturise them more frequently. Hence, they do not tolerate drying agents well and the rash can be worsened by them.

Perioral dermatitis is also known by other names including rosacea-like dermatoses, periorofacial dermatitis and periorificial dermatitis.

Unlike rosacea which involves mainly the nose and cheeks, there is no telangiectasia in perioral dermatitis. Rosacea also has a tendency to be present in older people. Acne can be distinguished by the presence of comedones and by its wider distribution on the face and chest. There are no comedones in personal dermatitis.

Other skin diseases which may resemble perioral dermatitis include:

- Rosacea

- Acne vulgaris

- Seborrheic dermatitis

- Allergic contact dermatitis

- Irritant contact dermatitis

Lepidopterism is an irritant contact dermatitis caused by irritating caterpillar or moth hairs coming into contact with the skin or mucosa. When referring to the cause, moth dermatitis and caterpillar dermatitis are commonly used; Caripito itch (known as "papillonite" in French) is an older name referring to the moth dermatitis caused by some "Hylesia" species.

Diagnosis of nummular dermatitis largely clinical. Biopsies are typically not necessary, and cannot be used to rule out other atopic dermatitis or other eczemas. However, patch testing may be employed to rule out irritants (contact dermatitis) as a cause. In children, nummular dermatitis is commonly confused with tinea corporis.

Plasma cell cheilitis is a very rare presentation of a condition which more usually occurs on the gingiva (termed "plasma cell gingivitis") or sometimes the tongue. Plasma cell cheilitis appears as well defined, infiltrated, dark red plaque with a superficial lacquer-like glazing. Plasma cell cheilitis usually involves the lower lip. The lips appear dry, atrophic and fissured. Angular cheilitis is sometimes also present.

Papular mucinosis is chronic and may be progressive. The dermal layer of the skin breaks out into small and solid bumps, usually conical in shape and measured from 2 to 4 mm or sometimes flat-topped papules. Unlike pustules, these bumps do not contain pus. Instead they contain mucin, a substance of mucus, the body's natural and protective lubricant found in saliva and epithelial cells in lungs and the sensitive part of the nose. They usually come in clusters such as linear arrays. Less frequently, urticarial, nodular, or sometimes annular lesions may be appreciated. The dorsal aspect of the hands, face, elbows, and extensor portions of the extremities are most frequently affected. Mucosal lesions are absent. The coalescence of papules on the face, particularly on the glabella, results in longitudinal folding and gives the appearance of a leonine facies.

In scleromyxedema, symptoms can occur on larger part of the body. Erythema and scleroderma-like induration occurs on the skin. In addition, the mobility of the lips, hands, arms, and legs is reduced. Proximal myopathy, inflammatory polyarthritis, central nervous system symptoms, esophageal aperistalsis, and hoarseness are among the notable systemic symptoms. If viscera is involved, the disease will be fatal. The dermatoneuro syndrome is a rare neurological complication of the disease presenting with fever, seizures and altered mental status.

Acneiform eruptions are a group of dermatoses including acne vulgaris, rosacea, folliculitis, and perioral dermatitis. Restated, acneiform eruptions are follicular eruptions characterized by papules and pustules resembling acne.

The hybrid term "acneiform", literally, refers to an appearance similar to acne.

The terminology used in this field can be complex, and occasionally contradictory. Some sources consider acne vulgaris part of the differential diagnosis for an acneiform eruption. Other sources classified acne vulgaris under acneiform eruption. MeSH explicitly excludes perioral dermatitis from the category of "acneiform eruptions", though it does group acneiform eruptions and perioral dermatitis together under "facial dermatoses".

Perioral dermatitis is a type of skin rash. Symptoms include multiple small (1–2 mm) bumps and blisters with sometimes background redness and scale, localized to the skin around the mouth and nostrils. Less commonly the eyes and genitalia may be involved. It can be persistent or recurring and resembles particularly rosacea and to some extent acne and allergic dermatitis. The term dermatitis is a misnomer because this is not an eczematous process.

The cause is unclear. Topical steroids are associated with the condition and moisturizers and cosmetics may contribute. The underlying mechanism may involve blockage of the skin surface followed by subsequent excessive growth of skin flora. Fluorinated toothpaste and some micro-organisms including candida may also worsen the condition, but their roles in this condition is unclear. It is considered a disease of the hair follicle with biopsy samples showing microscopic changes around the hair follicle. Diagnosis is based on symptoms.

Treatment is typically by stopping topical steroids, changing cosmetics, and in more severe cases, taking tetracyclines by mouth. Stopping steroids may initially worse the rash. The condition is estimated to affect 0.5-1% of people a year in the developed world. Up to 90% of those affected are women between the ages of 16 and 45 years, though it also affects children and the elderly, and has an increasing incidence in men.

Digital dermatitis appears as lesions which initially looks like raw, red, oval ulcer on the back of the heel. These lesions develop raised, hair-like projections or wart-like lesions, and some may extend up between the claws or appear on the front of the foot.

A scoring system was developed to classify the different stages of digital dermatitis, the M-stages system, where "M" stands for Mortellaro. The different stages are described as: M0, healthy skin; M1, early stage, skin defect < 2 cm diameter; M2, acute active ulcerative lesion; M3, healing stage, lesion covered with scab-like material; M4, chronic stage, that may be dyskeratotic (mostly thickened epithelium) or proliferative or both.

Diagnosis is principally based on history and clinical signs. It is very rare that attempts are made to isolate the bacteria.