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

Discoid eczema (nummular eczema, exudative eczema, microbial eczema) is characterized by round spots of oozing or dry rash, with clear boundaries, often on lower legs. It is usually worse in winter. Cause is unknown, and the condition tends to come and go. (ICD-10 L30.0)

Venous eczema (gravitational eczema, stasis dermatitis, varicose eczema) occurs in people with impaired circulation, varicose veins, and edema, and is particularly common in the ankle area of people over 50. There is redness, scaling, darkening of the skin, and itching. The disorder predisposes to leg ulcers. (ICD-10 I83.1)

Irritant diaper dermatitis is a generic term applied to skin rashes in the diaper area that are caused by various skin disorders and/or irritants.

Generic "diaper rash" or "irritant diaper dermatitis" (IDD) is characterized by joined patches of erythema and scaling mainly seen on the surfaces, with the skin folds spared.

Diaper dermatitis with secondary bacterial or fungal involvement tends to spread to surfaces (i.e. skin folds), as well as convex surfaces, and often exhibits a central red, beefy erythema with satellite pustules around the border.

It is usually considered a form of irritant contact dermatitis. The word "diaper" is in the name not because the diaper itself causes the rash but rather because the rash is associated with diaper use, being caused by the materials trapped by the diaper (usually feces). Allergic contact dermatitis has also been suggested, but there is little evidence for this cause. In adults with incontinence (fecal, urinary, or both), the rash is sometimes called incontinence-associated dermatitis (IAD).

The term diaper candidiasis is used when a fungal origin is identified. The distinction is critical because the treatment (antifungals) is completely different.

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.

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.

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.

People with AD often have dry and scaly skin that spans the entire body, except perhaps the diaper area, and intensely itchy red, splotchy, raised lesions to form in the bends of the arms or legs, face, and neck.

AD commonly occurs on the eyelids where signs such as Dennie-Morgan infraorbital fold, infra-auricular fissure, periorbital pigmentation can be seen. Post-inflammatory hyperpigmentation on the neck gives the classic 'dirty neck' appearance. Lichenification, excoriation and erosion or crusting on the trunk may indicate secondary infection. Flexural distribution with ill-defined edges with or without hyperlinearily on the wrist, finger knuckles, ankle, feet and hand are also commonly seen.

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

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.

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.

Seborrhoeic dermatitis' symptoms appear gradually, and usually the first signs are flaky skin and scalp. Symptoms occur most commonly anywhere on the skin of the scalp, behind the ears, on the face, and in areas where the skin folds. Flakes may be yellow, white or grayish. Redness and flaking may also occur on the skin near the eyelashes, on the forehead, around the sides of the nose, on the chest, and on the upper back.

In more severe cases, yellowish to reddish scaly pimples appear along the hairline, behind the ears, in the ear canal, on the eyebrows, on the bridge of the nose, around the nose, on the chest, and on the upper back.

Commonly, patients experience mild redness, scaly skin lesions and in some cases hair loss. Other symptoms include patchy scaling or thick crusts on the scalp, red, greasy skin covered with flaky white or yellow scales, itching, soreness and yellow or white scales that may attach to the hair shaft.

Seborrhoeic dermatitis can occur in infants younger than three months and it causes a thick, oily, yellowish crust around the hairline and on the scalp. Itching is not common among infants. Frequently, a stubborn diaper rash accompanies the scalp rash. Usually, when it occurs in infants the condition resolves itself within days and with no treatment.

In adults, symptoms of seborrhoeic dermatitis may last from a few weeks, to years. Many patients experience alternating periods of inflammation. The condition is referred to a specialist when self-care has proven unsuccessful.

The signs and symptoms of dandruff are an itchy scalp and flakiness. Red and greasy patches of skin and a tingly feeling on the skin are also symptoms.

Cradle cap is seborrheic dermatitis that affects infants. It presents on the scalp as greasy patches of scaling, which appear thick, crusty, yellow, white or brown. The affected regions are not usually itchy and do not bother the child. Other affected areas can include the eyelids, ear, around the nose, and in the groin. Hair loss can also occur.

Lip lickers dermatitis, popularly known as perioral dermatitis, is an Irritant contact dermatitis on and around the lips due to saliva from repetitive lip licking. Involving children more than adults, the resulting papules, scaling, erythema and occasional fissures and crusting make a well-defined ring around the lips. The rash extends as far as the tongue can reach and frequently spares the angle of the mouth. Unlike periorificial dermatitis, the vermillion border of the lip is often involved and the treatment is simple moisturisers.

The cause of AD is not known, although there is some evidence of genetic, environmental, and immunologic factors.

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.

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.

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.

Contact dermatitis is a localized rash or irritation of the skin caused by contact with a foreign substance. Only the superficial regions of the skin are affected in contact dermatitis. Inflammation of the affected tissue is present in the epidermis (the outermost layer of skin) and the outer dermis (the layer beneath the epidermis).

Contact dermatitis results in large, burning, and itchy rashes. These can take anywhere from several days to weeks to heal. This differentiates it from contact urticaria (hives), in which a rash appears within minutes of exposure and then fades away within minutes to hours. Even after days, contact dermatitis fades only if the skin no longer comes in contact with the allergen or irritant. Chronic contact dermatitis can develop when the removal of the offending agent no longer provides expected relief.

Irritant dermatitis is usually confined to the area where the trigger actually touched the skin, whereas allergic dermatitis may be more widespread on the skin. Symptoms of both forms include the following:

- Red rash. This is the usual reaction. The rash appears immediately in irritant contact dermatitis; in allergic contact dermatitis, the rash sometimes does not appear until 24–72 hours after exposure to the allergen.

- Blisters or wheals. Blisters, wheals (welts), and urticaria (hives) often form in a pattern where skin was directly exposed to the allergen or irritant.

- Itchy, burning skin. Irritant contact dermatitis tends to be more painful than itchy, while allergic contact dermatitis often itches.

While either form of contact dermatitis can affect any part of the body, irritant contact dermatitis often affects the hands, which have been exposed by resting in or dipping into a container (sink, pail, tub, swimming pools with high chlorine) containing the irritant.

Eyelid dermatitis is commonly related to atopic dermatitis or allergic contact dermatitis. Volatile substances, tosylamide, epoxy hardeners, insect sprays, and lemon peel oil may be implicated, with many cases of eyelid contact dermatitis being caused by substances transferred by the hands to the eyelids.

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".

Dandruff is a skin condition that affects mainly the scalp. Symptoms include flaking and sometimes mild itchiness. It can result in social or self-esteem problems. A more severe form of the condition, which includes inflammation of the skin, is known as seborrheic dermatitis.

The cause is unclear but believed to involve a number of genetic and environmental factors. The condition may worsen in the winter. It is not due to poor hygiene. The underlying mechanism involves the over growth of skin cells. Diagnosis is based on symptoms.

There is no known cure. The typical treatment is with antifungal cream such as ketoconazole. Dandruff affects about half of adults. Onset is usually at puberty. Males are more often affected than females. Rates decrease after the age of 50.

Cradle cap is a yellowish, patchy, greasy, scaly and crusty skin rash that occurs on the scalp of recently born babies. It is usually not itchy and does not bother the baby. Cradle cap most commonly begins sometime in the first three months but can occur in later years. Similar symptoms in older children are more likely to be dandruff than cradle cap. The rash is often prominent around the ear, the eyebrows or the eyelids. It may appear in other locations as well, where it is called seborrhoeic dermatitis rather than cradle cap. Some countries use the term "pityriasis capitis" for cradle cap. It is extremely common, with about half of all babies affected. Most of them have a mild version of the disorder. Severe cradle cap is rare.

Seborrhoeic dermatitis, also known as seborrhea, is a long term skin disorder. Symptoms include red, scaly, greasy, itchy, and inflamed skin. Often the scalp, face, and chest are affected. It can result in social or self-esteem problems. In babies, when the scalp is primarily involved, it is called cradle cap. Dandruff is a milder form of the condition, without associated inflammation.

The cause is unclear but believed to involve a number of genetic and environmental factors. Risk factors include poor immune function, Parkinson disease, epilepsy, and Down syndrome. The condition may worsen with stress or during the winter. It is not a result of poor hygiene. Diagnosis is typically based on the symptoms.

The typical treatment is antifungal cream and anti-inflammatory agents. Specifically ketoconazole or ciclopirox are effective. It is unclear if other antifungals, such as miconazole, are equally effective as they have been poorly studied. Other options may include coal tar and phototherapy.

The condition is most common in those around the age of 50, during puberty, and among those less than three months old. In adults about 2% of people are affected. Males are more often affected than females. Up to 40% of babies may be affected to some degree.