A common cause of lick granuloma appears to be psychological, related to stress, anxiety, separation anxiety, boredom, or compulsiveness. Lick granulomas are especially seen in large active dogs left alone for long periods of time. It is often considered to be a form of canine obsessive-compulsive disorder.

But other less common causes include bacterial or fungal infections, trauma causing nerve damage, allergies, or joint disease. Hot spots may also lead to the formation of lick granulomas.

Many large breed dogs appear to be predisposed, as well as golden retrievers and other bird dogs. Most of the dogs with the condition are over five years of age. Seventy percent of the time it occurs on one of the dog's left legs. Arthritic and mobility problems in older dogs give them more time to lick and over-groom themselves.

Frequent formations of lick granulomas in the same area due to the constant licking will cause hardening, callous formation, hair loss (the hair may stop growing back), and hyperpigmentation to that area. The condition becomes a vicious cycle – erosion of the skin from licking leads to pain and itching, which leads to more licking. Lick granulomas sometimes become infected with bacteria, causing abscessed areas or fistulous tracts (furuncles).

Treatment of the primary cause, if known, is essential.

In psychogenic cases, dealing with psychological factors is most important. Factors should be identified such as being left alone all day, being confined, and changes in the household. Correction of these causes may include increased walks, avoiding confinement, and more interaction in the home. Some veterinarians have proposed that diet can affect compulsive behaviors in dogs.

Drugs may be used until behavior modification has had time to take effect. Antidepressants are most commonly used, including doxepin, amitriptyline, fluoxetine, and clomipramine. If the psychological factors are not corrected, the pet will usually relapse after the drugs are discontinued. Endorphin blockers such as naltrexone can be used to reduce addiction to licking, or endorphin substitutes such as hydrocodone may decrease the urge to lick.

The animal should be tested for allergies, and treated accordingly if positive (fatty acids, antihistamines, hypoallergic diet, etc.). It may also be necessary to check thyroid levels, as hypothyroidism seems to play a role in some cases, particularly in black Labrador retrievers; thyroid medication often will resolve the problem if it's due to hypothyroidism.

The interaction between fecal enzyme activity and IDD explains the observation that infant diet and diaper rash are linked because fecal enzymes are in turn affected by diet. Breast-fed babies, for example, have a lower incidence of diaper rash, possibly because their stools have higher pH and lower enzymatic activity. Diaper rash is also most likely to be diagnosed in infants 8–12 months old, perhaps in response to an increase in eating solid foods and dietary changes around that age that affect fecal composition. Any time an infant’s diet undergoes a significant change (i.e. from breast milk to formula or from milk to solids) there appears to be an increased likelihood of diaper rash.

The link between feces and IDD is also apparent in the observation that infants are more susceptible to developing diaper rash after treating with antibiotics, which affect the intestinal microflora. Also, there is an increased incidence of diaper rash in infants who have suffered from diarrhea in the previous 48 hours, which may be because fecal enzymes such as lipase and protease are more active in feces which have passed rapidly through the gastrointestinal tract.

Although wetness alone has the effect of macerating the skin, softening the stratum corneum, and greatly increasing susceptibility to friction injury, urine has an additional impact on skin integrity because of its effect on skin pH. While studies show that ammonia alone is only a mild skin irritant, when urea breaks down in the presence of fecal urease it increases pH because ammonia is released, which in turn promotes the activity of fecal enzymes such as protease and lipase. These fecal enzymes increase the skin's hydration and permeability to bile salts which also act as skin irritants.

There is no detectable difference in rates of diaper rash in conventional disposable diaper wearers and reusable cloth diaper wearers. "Babies wearing superabsorbent disposable diapers with a central gelling material have fewer episodes of diaper dermatitis compared with their counterparts wearing cloth diapers. However, keep in mind that superabsorbent diapers contain dyes that were suspected to cause allergic contact dermatitis (ACD)." Whether wearing cloth or disposable diapers they should be changed frequently to prevent diaper rash, even if they don't feel wet. To reduce the incidence of diaper rash, disposable diapers have been engineered to pull moisture away from the baby's skin using synthetic non-biodegradable gel. Today, cloth diapers use newly available superabsorbent microfiber cloth placed in a pocket with a layer of light permeable material that contacts the skin. This design serves to pull moisture away from the skin in to the microfiber cloth. This technology is used in most major pocket cloth diapers brands today.

Several drugs may cause AC as a side effect, by various mechanisms, such as creating drug-induced xerostomia. Various examples include isotretinoin, indinavir, and sorafenib. Isotretinoin (Accutane), an analog of vitamin A, is a medication which dries the skin. Less commonly, angular cheilitis is associated with primary hypervitaminosis A, which can occur when large amounts of liver (including cod liver oil and other fish oils) are regularly consumed or as a result from an excess intake of vitamin A in the form of vitamin supplements. Recreational drug users may develop AC. Examples include cocaine, methamphetamines, heroin, and hallucinogens.

Cosmetics play an important role as causal factors for perioral dermatitis. Regular generous applications of moisturising creams cause persistent hydration of the horny layer causing impairment and occlusion of the barrier function, irritation of the hair follicle and proliferation of skin flora. Combining this with night cream and foundation significantly increases risk of perioral dermatitis by 13-fold.

Topical corticosteroids may lead to increase micro-organism density in the hair follicle. The role of infectious agents such as Candida species, Demodex folliculorum, and fusiform bacteria has not been confirmed.

Atopy is a hereditary and chronic (lifelong) allergic skin disease. Signs usually begin between 6 months and 3 years of age, with some breeds of dog, such as the Golden Retriever showing signs at an earlier age. Dogs with atopic dermatitis are itchy, especially around the eyes, muzzle, ears and feet. In severe cases the irritation is generalised. If the allergens are seasonal, the signs of irritation are similarly seasonal. Many dogs with house dust mite allergy have perennial disease. Some of the allergens associated with atopy in dogs include pollens of trees, grasses and weeds, as well as molds and House dust mite. Ear and skin infections with the bacteria "Staphylococcus pseudintermedius" and the yeast "Malassezia pachydermatis" are common secondary to atopic dermatitis.

Food allergy can be associated with identical signs and some authorities consider food allergy to be a type of atopic dermatitis.

Diagnosis of atopic dermatitis is by elimination of other causes of irritation including fleas, scabies and other parasites such as Cheyletiella and lice. Food allergy can be identified through the use of elimination diet trials in which a novel or hydrolysed protein diet is used for a minimum of 6 weeks and allergies to aeroallergens can be identified using intradermal allergy testing and/or blood testing (allergen-specific IgE ELISA).

Treatment includes avoidance of the offending allergens if possible, but for most dogs this is not practical or effective. Other treatments modulate the adverse immune response to allergens and include antihistamines, steroids, ciclosporin and immunotherapy (a process in which allergens are injected to try to induce tolerance). In many cases shampoos, medicated wipes and ear cleaners are needed to try to prevent the return of infections.

New research into T-cell receptor peptides and their effects on dogs with severe, advanced atopic dermatitis are being investigated.

Vitamins are one of many of the nutritional factors that change the outward appearance of a dog. The fat soluble vitamins A and E play a critical role in maintaining skin health. Vitamin A, which can also be supplemented as beta-carotene, prevents the deterioration of epithelial tissues associated with chronic skin diseases and aging. A deficiency in vitamin A can lead to scaly of skin and other dermatisis related issues like alopecia Vitamin E is an antioxidant. Vitamin E neutralizes free radicals that accumulate in highly proliferative cells like skin and prevent the deterioration of fibrous tissue caused by these ionized molecules. There are also a couple of water-soluble vitamins that contribute to skin health. Riboflavin (B2) is a cofactor to the metabolism of carbohydrates and when deficient in the diet leads to cracked, brittle skin. Biotin (B7) is another B vitamin that, when deficient, leads to alopecia.

Several different nutritional deficiency states of vitamins or minerals have been linked to AC. It is thought that in about 25% of people with AC, iron deficiency or deficiency of B vitamins are involved. Nutritional deficiencies may be a more common cause of AC in Third World countries. Chronic iron deficiency may also cause koilonychia (spoon shaped deformity of the fingernails) and glossitis (inflammation of the tongue). It is not completely understood how iron deficiency causes AC, but it is known that it causes a degree of immunocompromise (decreased efficiency of the immune system) which may in turn allow an opportunistic infection of candida. Vitamin B2 deficiency (ariboflavinosis) may also cause AC, and other conditions such as redness of mucous membranes, magenta colored glossitis (pink inflammation of the tongue). Vitamin B5 deficiency may also cause AC, along with glossitis, and skin changes similar to seborrhoeic dermatitis around the eyes, nose and mouth. Vitamin B12 deficiency is sometimes responsible for AC, and commonly occurs together with folate deficiency (a lack of folic acid), which also causes glossitis and megaloblastic anemia. Vitamin B3 deficiency (pellagra) is another possible cause, and in which other association conditions such as dermatitis, diarrhea, dementia and glossitis can occur. Biotin (vitamin B7) deficiency has also been reported to cause AC, along with hair loss (alopecia) and dry eyes. Zinc deficiency is known to cause AC. Other symptoms may include diarrhea, alopecia and dermatitis. Acrodermatitis enteropathica is an autosomal recessive genetic disorder causing impaired absorption of zinc, and is associated with AC.

In general, these nutritional disorders may be caused by malnutrition, such as may occur in alcoholism or in poorly considered diets, or by malabsorption secondary to gastrointestinal disorders (e.g. Coeliac disease or chronic pancreatitis) or gastrointestinal surgeries (e.g. pernicious anemia caused by ileal resection in Crohn's disease).

With no particular affinity to any particular ethnic group, seen in all age groups and equally amongst males and females, the precise prevalence is not known.

This is a rare inflammatory condition of the minor salivary glands, usually in the lower lip, which appears swollen and everted. There may also be ulceration, crusting, abscesses, and sinus tracts. It is an acquired disorder, but the cause is uncertain. Suspected causes include sunlight, tobacco, syphilis, poor oral hygiene and genetic factors. The openings of the minor salivary gland ducts become inflamed and dilated, and there may be mucopurulent discharge from the ducts. A previous classification suggested dividing cheilitis into 3 types based on severity, with the later stages involving secondary infection with bacteria, and increased ulceration, suppuration and swelling: Type 1, Simple; Type 2, Superficial suppurative ("Baelz's disease"); and Type 3, Deep suppurative ("cheilitis glandularis epostemetosa"). Cheilitis glandularis usually occurs in middle-aged and elderly males, and it carries a risk of malignant transformation to squamous cell carcinoma (18% to 35%). Preventative treatment such as vermilionectomy ("lip shave") is therefore the treatment of choice.

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.

Rosin, the material commonly used to wax string instruments is known to cause allergic contact dermatitis in musicians. Nickel, a metal found in musical instruments causes allergic contact dermatitis on the fingers and hands of string instrumentalists and in the lip and neck of wind instrumentalists. Wind instrumentalists with lip and neck infection should switch to gold or plastic mouthpieces if allergic dermatitis occurs. (R)-4-methoxydalbergione present in rosewood may cause allergic contact dermatitis in violinists. Cane reed (causing chelitis in saxophone players), propolis (a wax used to close structural gaps in musical instruments), paraphenylenediamine (used to polish musical instruments) and potassium dichromate (tanning agent to the skin of the harp) also cause allergic contact dermatitis in musicians.

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.

The diagnosis of lip licker's dermatitis is from the history and inspection of the rash. It is important to distinguish it from allergic contact dermatitis and perioral dermatitis which is characterised by papule in the perioral area, sparing of the vermillion border and worsened by topical steroids.

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 prevalence of nummular dermatitis in the United States is approximately 2 per 1,000. It is considered a disease of adulthood, for it is rare in children.

Many contact sensitizers or irritants are known to cause contact dermatitis superimposed on nummular dermatitis. Studies have implicated nickel, cobalt, chromate, and fragrance as likely culprits. Xerosis, or dehydration of skin is also a likely cause. Infection with "Staphylococcus aureus" bacteria or "Candida" may also play a role.

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.

There is no good evidence that a mother's diet during pregnancy, the formula used, or breastfeeding changes the risk. There is tentative evidence that probiotics in infancy may reduce rates but it is insufficient to recommend its use.

People with eczema should not get the smallpox vaccination due to risk of developing eczema vaccinatum, a potentially severe and sometimes fatal complication.

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.

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.

Also termed "cheilitis exfoliativa" or "tic de levres", is an uncommon inflammatory condition of the vermilion zone of the lips, which are painful and crusted. There is continuous production and desquamation (shedding) of thick, brown scales of keratin. The keratin layer of the epidermis of the lips experiences a faster growth and death rate than normal and desquamates. When these scales are removed, a normal appearing lip is revealed beneath, although there may be associated erythema and edema. The condition has not yet been attributed to any particular cause. Rarely are infections to blame. In some individuals, there is an association with stress, anxiety, depression or personality disorders. In one report, 87% of individuals had some form of psychiatric disturbance, and 47% had thyroid dysfunction, which in turn can cause psychiatric conditions like depression.

Some cases of exfoliative cheilitis are thought to represent factitious damage, termed "factitious cheilitis" or "artifactual cheilitis", and are related to repetitive lip picking or licking habits. This appears as crusting and ulceration caused by repetitive chewing and sucking of the lips. Some consider habitual lip licking or picking to be a form of nervous tic. This habit is sometimes termed "perlèche" (derived from the French word "pourlècher" meaning "to lick one’s lips"). Factitious cheilitis is significantly more common in young females.

Exfoliative cheilitis has also been linked to HIV/AIDS. Management consists mostly of keeping the lips moist and the application of topical corticosteroids ranging from hydrocortisone to clobetasol. There have also been reports of using topical tacrolimus ointment.

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.