Characteristics may vary according to the subtype of pustular psoriasis. For example, it can be localized, commonly to the hands and feet (localized pustular psoriasis), or generalized with widespread patches occurring randomly on any part of the body (generalized pustular psoriasis). However, all forms of pustular psoriasis share in common the presence of red and tender blotchy skin covered with pustules.

Pustular psoriasis can be localized, commonly to the hands and feet (palmoplantar pustulosis), or generalized with widespread patches occurring randomly on any part of the body. Acrodermatitis continua is a form of localized psoriasis limited to the fingers and toes that may spread to the hands and feet. Pustulosis palmaris et plantaris is another form of localized pustular psoriasis similar to acrodermatitis continua with pustules erupting from red, tender, scaly skin found on the palms of the hands and the soles of the feet.

Generalized pustular psoriasis (GPP) is also known as (von Zumbusch) acute generalized pustular psoriasis in acute cases, and as impetigo herpetiformis during pregnancy. GPP is a rare and severe form of psoriasis that may require hospitalization. This form of psoriasis is characterized by an acute onset of numerous pustules on top of tender red skin. This skin eruption is often accompanied by a fever, muscle aches, nausea, and an elevated white blood cell count. Annular pustular psoriasis (APP), a rare form of GPP, is the most common type seen during childhood. APP tends to occur in women more frequently than in men, and is usually less severe than other forms of generalized pustular psoriasis such as impetigo herpetiformis. This form of psoriasis is characterized by ring-shaped plaques with pustules around the edges and yellow crusting. APP most often affects the torso, neck, arms, and legs.

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.

Dyshidrosis has been described as having the following characteristics:

- Itchiness of the palms or soles, followed the a sudden development of intensely itchy small blisters on the sides of the fingers, the palms or the feet.

- These blisters are often described as having a "tapioca pudding" appearance.

- After a few weeks, the small blisters eventually disappear as the top layer of skin falls off.

- These eruptions do not occur elsewhere on the body.

- The eruptions may be symmetrical.

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.

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.

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.

Symptoms of miliaria include small red rashes, called papules, which are irritated and itchy. These may simultaneously occur at a number of areas on a sufferer's body, the most common including the upper chest, neck, elbow creases, under the breasts and under the scrotum. Other areas include skin folds, areas of the body that may rub against clothing, such as the back, chest, and stomach, etc. A related and sometimes simultaneous condition is folliculitis, where hair follicles become plugged with foreign matter, resulting in inflammation.

The symptoms relating to miliaria should not be confused with shingles as they can be very similar. Shingles will restrict itself to one side of the body but also has a rash-like appearance. It is also accompanied by a prickling sensation and pain throughout the region. Those who suspect they have shingles and not miliaria should seek medical advice immediately as the sooner antivirals are taken, the better.

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.

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 most superficial obstruction (with the most mild clinical presentation), is known as "miliaria crystalline"; instead of a rash, the patient presents with multiple tiny blister-like lesions that look like beads of perspiration and essentially cause no symptoms. "Miliaria crystalline" is also known as "Miliaria crystallina," and "Sudamina". The superficial vesicles are not associated with an inflammatory reaction.

Signs include facial redness, small and superficial dilated blood vessels on facial skin, papules, pustules, and swelling.

Pustular psoriasis is classified into two major forms: localized and generalized pustular psoriasis. Within these two categories there are several variants:

In glandular rosacea, men with thick sebaceous skin predominate, a disease in which the papules are edematous, the pustules often 0.5 to 1.0 cm in size, with nodulocystic lesions often present.

People burdened with LSC report pruritus, followed by uncontrollable scratching of the same body region, excessively. Most common sites of LSC are the sides of the neck, the scalp, ankles, vulva, pubis, scrotum, and extensor sides of the forearms. However, due to the stigma associated with chronic scratching, some patients will not admit to chronic rubbing or abrasion. The skin may become thickened and hyperpigmented (lichenified) as a direct result of chronic exoriation. Typically this period of increased scratching is associated with stressors.

Although lichen planus can present with a variety of lesions, the most common presentation is as a well defined area of purple-coloured, itchy, flat-topped papules with interspersed lacy white lines (Wickham's striae). This description is known as the characteristic "6 Ps" of lichen planus: planar (flat-topped), purple, polygonal, pruritic, papules, and plaques. This rash, after regressing, is likely to leave an area of hyperpigmentation that slowly fades. That said, a variety of other lesions can also occur.

Variants of cutaneous lichen planus are distinguished based upon the appearance of the lesions and/or their distribution. Lesions can affect the:

- Extremities (face, dorsal hands, arms, and nape of neck). This is more common in Middle Eastern countries in spring and summer, where sunlight appears to have a precipitating effect.

- Palms and soles

- Intertriginous areas of the skin. This is also known as "Inverse lichen planus."

- Nails characterized by irregular longitudinal grooving and ridging of the nail plate, thinning of the nail plate, pterygium formation, shedding of the nail plate with atrophy of the nail bed, subungual keratosis, longitudinal erthronychia (red streaks), and subungual hyperpigmentation. A sand-papered appearance is present in around 10% of individuals with nail lichen planus.

- Hair and Scalp. The scalp is rarely affected by a condition known as lichen planopilaris, acuminatus, follicular lichen planus, and peripilaris, characterised by violaceous, adherent follicular scale with progressive scarring alopecia. While lichen planus and lichen planopilaris may occur together, aside from sharing the term ‘lichen’ and revealing inflammation on skin biopsy, there is neither established data on their co-occurrence nor data to suggest a common etiology. Lichen planopilaris is considered an orphan disease with no definitive prevalence data and no proven effective treatments.

Other variants may include:

- "Lichen planus pemphigoides" characterized by the development of tense blisters atop lesions of lichen planus or the development vesicles de novo on uninvolved skin.

- "Keratosis lichenoides chronica" (also known as "Nekam's disease") is a rare dermatosis characterized by violaceous papular and nodular lesions, often arranged in a linear or reticulate pattern on the dorsal hands and feet, extremities, and buttock, and some cases manifest by sorrheic dermatitis-like eruption on the scalp and face; also palmo plantar keratosis has been reported.

- "Lichenoid keratoses" (also known as "Benign lichenoid keratosis," and "Solitary lichen planus") is a cutaneous condition characterized by brown to red scaling maculopapules, found on sun-exposed skin of extremities. Restated, this is a cutaneous condition usually characterized by a solitary dusky-red to violaceous papular skin lesion.

- "Lichenoid dermatitis" represents a wide range of cutaneous disorders characterized by lichen planus-like skin lesions.

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)

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.

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)

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.

Dyshidrosis, is a type of dermatitis, that is characterized by itchy blisters on the palms of the hands and bottoms of the feet. Blisters are generally one to two millimeters in size and heal over three weeks. However, they often recur. Redness is not usually present. Repeated attacks may result in fissures and skin thickening.

The cause is unknown. Triggers may include allergens, physical or mental stress, frequent hand washing, or metals. Diagnosis is typically based on what it looks like and the symptoms. Allergy testing and culture may be done to rule out other problems. Other conditions that produce similar symptoms include pustular psoriasis and scabies.

Avoiding triggers may be useful as may a barrier cream. Treatment is generally with steroid cream. High strength steroid creams may be required for the first week or two. Antihistamines may be used to help with the itch. If this is not effective steroid pills, tacrolimus, or psoralen plus ultraviolet A (PUVA) may be tried.

About 1 in 2,000 people are affected in Sweden. Males and females appear to be affected equally. It explains about one in five cases of hand dermatitis. The first description was in 1873. The name comes from the word "dyshidrotic," meaning "difficult sweating," as problems with sweating was once believed to be the cause.

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.

Lichen simplex chronicus (LSC) (also known as "Neurodermatitis") is a skin disorder characterized by chronic itching and scratching. The constant scratching causes thick, leathery, darkened, (lichenified) skin. This condition is associated with many factors, including the scratch-itch cycle, psychological stressors, and atopy. LSC is more common between ages 35 and 50 and is seen approximately twice as often in women compared to men.

Pemphigus vegetans is a localized form of pemphigus vulgaris.

in which there is a localized vegetating papillomatous response. The eroded areas do not heal like usual but form papillomatous growth and vegetation.

Accounts for 1-2% of pemphigus cases and is a relatively benign variant of pemphigus vulgaris.

Two forms are recognized:

- "Pemphigus vegetans of Neumann" is a localized disease of pemphigus vulgaris slightly more extensive than pemphigus vegetans of Hallopeau. This type is more common and characterized by early lesions similar to Pemphigus Vulgaris with large bullae and erosive areas. Healing is through formation of granulation tissue. It is named for the Austrian Dermatologist, Isidor Neumann.

- "Pemphigus vegetans of Hallopeau" is a disease of localized pemphigus vulgaris. It is named for François Henri Hallopeau. This type is less aggressive and has pustules not bullae. These pustules heal by verrucios hyperkeratotic vegetations.