Lichen planus has a unique microscopic appearance that is similar between cutaneous, mucosal and oral. A Periodic acid-Schiff stain of the biopsy may be used to visualise the specimen. Histological features seen include:

- thickening of the stratum corneum both with nuclei present (parakeratosis) and without (orthokeratosis). Parakeratosis is more common in oral variants of lichen planus.

- thickening of the stratum granulosum

- thickening of the stratum spinosum (acanthosis) with formation of colloid bodies (also known as Civatte bodies, Sabouraud bodies) that may stretch down to the lamina propria.

- liquefactive degeneration of the stratum basale, with separation from the underlying lamina propria, as a result of desmosome loss, creating small spaces (Max Joseph spaces).

- Infiltration of T cells in a band-like pattern into the dermis "hugging" the basal layer.

- Development of a "saw-tooth" appearance of the rete pegs, which is much more common in non-oral forms of lichen planus.

The differential diagnosis for OLP includes:

- Other oral vesiculo-ulcerative conditions such as Pemphigus vulgaris and Benign mucous membrane pemphigoid

- Lupus erythematosus, with lesions more commonly occur on the palate and appear as centrally ulcerated or erythematous with radiating white striae. In contrast, OLP and lichenoid reactions rarely occur on the palate, and the striae are randomly arranged rather than radial.

- Chronic ulcerative stomatitis

- Frictional keratosis and Morsicatio buccarum (chronic cheek biting)

- Oral leukoplakia

- Oral candidiasis

Visual diagnosis is made by the "stuck on" appearance, horny pearls or cysts embedded in the structure. Darkly pigmented lesions can be challenging to distinguish from nodular melanomas. Furthermore, thin seborrheic keratoses on facial skin can be very difficult to differentiate from lentigo maligna even with dermatoscopy. Clinically, epidermal nevi are similar to seborrheic keratoses in appearance. Epidermal nevi are usually present at or near birth. Condylomas and warts can clinically resemble seborrheic keratoses, and dermatoscopy can be helpful. On the penis and genital skin, condylomas and seborrheic keratoses can be difficult to differentiate, even on biopsy.

To date, the gold standard in the diagnosis of seborrheic keratosis is represented by the histolopathologic analysis of a skin biopsy.

Physicians can often diagnose keratosis pilaris simply by examining the skin; tests are usually not needed. However, a dermatologist can use dermoscopy to confirm the diagnosis and assess if a person with KP is responding to treatment. Physicians will often consider family history and the presence of symptoms when making the diagnosis. Those with this condition are generally encouraged to contact a physician if the bumps are bothersome and do not improve with over the counter lotions.

Physicians usually diagnose actinic keratosis by doing a thorough physical examination, through a combination of visual observation and touch. However a biopsy may be necessary when the keratosis is large in diameter, thick, or bleeding, in order to make sure that the lesion is not a skin cancer. Actinic keratosis and squamous cell carcinoma (SCC) can present similarly on physical exam, and many scientists argue that they are in fact simply different stages of the same condition. In addition to SCCs, AKs can be mistaken for other cutaneous lesions including seborrheic keratoses, basal cell carcinoma, lichenoid keratosis, porokeratosis, viral warts, inflammatory dermatoses, or melanoma.

A lesion biopsy is performed if the diagnosis remains uncertain after a clinical physical exam. The most common tissue sampling techniques include shave or punch biopsy. When only a portion of the lesion can be removed due to its size or location, the biopsy should sample tissue from the thickest area of the lesion, as SCCs are most likely to be detected in that area. If a shave biopsy is performed, it should extend through to the level of the dermis in order to provide sufficient tissue for diagnosis; ideally, it would extend to the mid-reticular dermis. Punch biopsy usually extends to the subcutaneous fat when the entire length of the punch blade is utilized.

There are several different types of keratosis pilaris, including "keratosis pilaris rubra" (red, inflamed bumps which can be on arms, head, legs), "keratosis pilaris alba" (rough, bumpy skin with no irritation), "keratosis pilaris rubra faceii" (reddish rash on the cheeks), and related disorders. Keratosis pilaris is commonly described in association with other dry skin conditions, such as ichthyosis vulgaris, xerosis and atopic dermatitis, including those of asthma and allergies.

Keratosis pilaris does not bear any known, long-term health implications, nor is it associated with increased mortality or morbidity. It is not related to goose bumps, which results from muscle contractions, except that both occur in the area where the hair shaft exits the skin.

Tissue biopsy is usually indicated to rule out other causes of white patches and also to enable a detailed histologic examination to grade the presence of any epithelial dysplasia. This is an indicator of malignant potential and usually determines the management and recall interval. The sites of a leukoplakia lesion that are preferentially biopsied are the areas that show induration (hardening) and erythroplasia (redness), and erosive or ulcerated areas. These areas are more likely to show any dysplasia than homogenous white areas.

Brush biopsy/exfoliative cytology is an alternative to incisional biopsy, where a stiff brush is scraped against the lining of the mouth to remove a sample of cells. This is then made into a smear which can be examined microscopically. Sometimes the biopsy site can be selected with adjunct methods which aim to highlight areas of dysplasia. Toluidine blue staining, where the dye is preferentially retained by dysplastic tissue, is sometimes used, but there is high false positive rate. Other methods involve the use of illuminescence, relying on either the property of normal autoflorescent molecules in mucosa such as collagen and keratin which is lost from areas of dysplasia or carcinoma under blue light, or by initially staining of the mucosa with toluidine blue or dilute acetic acid and examination under white light.

No treatment of seborrheic keratoses is necessary, except for aesthetic reasons. Since a slightly increased risk of localized infection caused by picking at the lesion has been described, if a lesion becomes itchy or irritated by clothing or jewelry, a surgical excision is generally recommended.

Small lesions can be treated with light electrocautery. Larger lesions can be treated with electrodesiccation and curettage, shave excision, or cryosurgery. When correctly performed, removal of seborrheic keratoses will not cause much visible scarring except in persons with dark skin tones.

Intertrigo can be diagnosed clinically by a medical professional after taking a thorough history and performing a detailed physical examination. Many other skin conditions can mimic intertrigo's appearance including erythrasmascabies, pyoderma, atopic dermatitis, candidiasis, and seborrheic dermatitis, and fungal infections of the superficial skin caused by "Tinea versicolor" or "Tinea corporis".

Tinea versicolor may be diagnosed by a potassium hydroxide (KOH) preparation and lesions may fluoresce copper-orange when exposed to Wood's lamp.

The differential diagnosis for tinea versicolor infection includes:

- Progressive macular hypomelanosis

- Pityriasis alba

- Pityriasis rosea

- Seborrheic dermatitis

- Erythrasma

- Vitiligo

- Leprosy

- Syphilis

- Post-inflammatory hypopigmentation

The annual malignant transformation rate of leukoplakia rarely exceeds 1%, i.e. the vast majority of oral leukoplakia lesions will remain benign. A number of clinical and histopathologic features are associated with varying degrees of increased risk of malignant transformation, although other sources argue that there are no universally accepted and validated factors which can reliably predict malignant change. It is also unpredictable to an extent if an area of leukoplakia will disappear, shrink or remain stable.

- Presence and degree of dysplasia (mild, moderate or severe/carcinoma in situ). Dysplasia is the most important predictor of malignant change, and about 10% of leukoplakia lesions show dysplasia when biopsied.

- Leukoplakia located on the floor of the mouth, the posterior and lateral tongue, and the retromolar areas (the region behind the wisdom teeth) have higher risk, whereas white patches in areas such as the top surface of the tongue and the hard palate do not have significant risk. Although these "high risk" sites are recognized, statistically, leukoplakia is more common on the buccal mucosa, alveolar mucosa, and the lower labial mucosa. Leukoplakia of the floor of the mouth and tongue accounts for over 90% of leukoplakias showing dysplasia or carcinoma on biopsy. This is thought to be due to pooling of saliva in the lower part of the mouth, exposing these areas to more carcinogens held in suspension.

- Red lesions (erythroplasia) and mixed red and white lesions (erythroleukoplakia/"speckled leukoplakia") have a higher risk of malignant change than homogenous leukoplakia.

- Verrucous or nodular areas have a higher risk.

- Although smoking increases risk of malignant transformation, smoking also causes many white patches with no dysplasia. This means that statistically, white patches in non smokers have a higher risk.

- Older people with white patches are at higher risk.

- Larger white patches are more likely to undergo malignant transformation than smaller lesions.

- White patches which have been present for a long period of time have higher risk.

- Persons with a positive family history of cancer in the mouth.

- Candida infection in the presence of dysplasia has a small increased risk.

- A change in the appearance of the white patch, apart from a change in the color, has a higher risk. Changes in the lesion such as becoming fixed to underlying tissues, ulceration, cervical lymphadenopathy (enlargement of lymph nodes in the neck), and bone destruction may herald the appearance of malignancy.

- White patches present in combination with other conditions that carry a higher risk (e.g. oral submucous fibrosis), are more likely to turn malignant.

- Although overall, oral cancer is more common in males, females with white patches are at higher risk than men.

The classification of exfoliative dermatitis into Wilson-Brocq (chronic relapsing), Hebra or pityriasis rubra (progressive), and Savill (self-limited) types may have had historical value, but it currently lacks pathophysiologic or clinical utility.

Patient presents with the following signs.

1. Hyperkeratotic papules present over the seborrheic area of the body.

2. V - shaped nicking present at the tip of the nails.

3. Red and white longitudinal nail lines.

Intertrigo is treated by addressing associated infections, by removing moisture from the site, and by using substances at the site to help maintain skin integrity. If the individual is overweight, losing weight may also help. Relapses of intertrigo are common.

Keeping the area of the intertrigo dry and exposed to the air can help prevent recurrences, as can removing moisture from the area using absorbent fabrics or body powders, including plain cornstarch and judiciously used antiperspirants.

Greases, oils, and barrier ointments, may help by protecting skin from moisture and from friction. Antifungal powders, most commonly clotrimazole 1%, may also be used in conjunction with a barrier ointment. Diaper rash ointment can also help.

Fungal infections associated with intertrigo may be treated with prescription antifungals applied directly to the skin (in most cases) or systemic antifungals, including fluconazole, nystatin, and griseofulvin.

Intertrigo is also a known symptom of vitamin B6 deficiency.

Even though there is no way to cure the disease itself, there are ways to dampen the symptoms. These include medical help in form of pills, and using heavy lotions and oils.

To maintain the good health of the skin after the symptoms have dampened the person with the disease are advised to go on normally with their lives but to take precautions while showering. This is to take shorter, colder baths than usual to not stress the skin. It is also known to help to use bar-soap, instead of a liquid body wash.

Keratosis (from "keratinocyte", the prominent cell type in the epidermis, and , abnormal) is a growth of keratin on the skin or on mucous membranes. More specifically, it can refer to:

- actinic keratosis (also known as solar keratosis)

- hydrocarbon keratosis

- keratosis pilaris (KP, also known as follicular keratosis)

- seborrheic keratosis

Actinic keratoses are pre-malignant growths. Seborrheic keratoses are not pre-malignant.

To help with cradle cap, parents can gently massage their baby's scalp with their fingers or a soft brush to loosen the scales. They may want to shampoo the baby's hair more frequently (no more than once a day), and after shampooing gently brush the baby's scalp with a soft brush or a terrycloth towel. Oil remedies can be used by rubbing a small amount of pure, plant-derived oil (coconut oil, pure olive oil, almond oil) on the baby's scalp and leaving it on for 15 minutes. After 15 minutes, gently comb out the flakes with a fine tooth comb or brush. Be sure to wash out all of the oil to avoid making the cradle cap worse.

For infants: in cases that are related to fungal infection, such as Tinea capitis, doctors may recommend a treatment application of clotrimazole (commonly prescribed for jock itch or athlete's foot) or miconazole (commonly prescribed for vaginal yeast infections).

For toddlers: doctors may recommend a treatment with a mild dandruff shampoo such as Selsun Blue or Neutrogena T-gel, even though the treatment may cause initial additional scalp irritation. A doctor may instead prescribe an antifungal soap such as ketoconazole (2%) shampoo, which can work in a single treatment and shows significantly less irritation than over-the-counter shampoos such as selenium disulfide shampoos, but no adequate and controlled study has been conducted for pediatric use as of 2010.

For adults: see the article on seborrheic dermatitis (the adult version of cradle cap).

This skin disease commonly affects adolescents and young adults, especially in warm and humid climates. The yeast is thought to feed on skin oils (lipids), as well as dead skin cells. Infections are more common in people who have seborrheic dermatitis, dandruff, and hyperhidrosis.

You have to treat the primary cause or the exacerbation may persisist and reincide.

Topical steroids are the primary category of medications used to treat exfoliative dermatitis (ED). A sedative antihistamine may be a useful adjunct for pruritic patients, since it helps patients to sleep at night, thus limiting nocturnal scratching and excoriations. Antimicrobial agents often are used if an infection is suspected to be precipitating or complicating exfoliative dermatitis. Other drugs specifically indicated for management of underlying cause of exfoliative dermatitis may be necessary.

DPN is not a premalignant condition nor is it associated with any underlying systemic disease. DPN lesions show no tendency to regress spontaneously, and often increase in size and number as an individual ages.

Dandruff scale is a cluster of corneocytes, which have retained a large degree of cohesion with one another and detach as such from the surface of the stratum corneum. A corneocyte is a protein complex that is made of tiny threads of keratin in an organised matrix. The size and abundance of scales are heterogeneous from one site to another and over time. Parakeratotic cells often make up part of dandruff. Their numbers are related to the severity of the clinical manifestations, which may also be influenced by seborrhea.

A 1992 study of 163 affected persons found that most patients had no other medical problems and most manage to lead a relatively normal life.

The diagnosis is normally made based upon the clinical appearance and history. Tissue biopsy is not usually indicated unless there are areas of ulceration or localized erythroplakia (red patches). The differential diagnosis is with other causes of white lesions (see leukoplakia for a more complete discussion). Specific conditions which can produce a similar appearance include Darier's disease, discoid lupus erythematosus, oral candidiasis, and oral lichen planus.

If a biopsy is taken, the histopathologic appearance is one of hyperkeratosis and acanthosis. There may be squamous metaplasia of excretory ducts, which results in the visible papules if the ducts become hyperplastic. Neutrophils may fill some ducts. It is characterized as a "fissured" or "dried mud" appearance from excess keratin production by cells. Dysplasia is rarely seen.

To prevent AC from developing, protective measures could be undertaken such as avoiding mid-day sun, or use of a broad-brimmed hat, lip balm with anti UVA and UVB ingredients (e.g. para-aminobenzoic acid), or sun blocking agents (e.g. zinc oxide, titanium oxide) prior to sun exposure.