Clinical diagnosis can be made with the naked eye using the ABCD guideline or by using dermatoscopy. An online-screening test is also available to help screen out benign moles.

It often requires a dermatologist to fully evaluate moles. For instance, a small blue or bluish-black spot, often called a blue nevus, is usually benign but often mistaken for melanoma. Conversely, a junctional nevus, which develops at the junction of the dermis and epidermis, is potentially cancerous.

A basic reference chart used for consumers to spot suspicious moles is found in the mnemonic A-B-C-D, used by institutions such as the American Academy of Dermatology and the National Cancer Institute. The letters stand for asymmetry, border, color, and diameter. Sometimes, the letter E (for elevation or evolving) is added. According to the American Academy of Dermatology, if a mole starts changing in size, color, shape or, especially, if the border of a mole develops ragged edges or becomes larger than a pencil eraser, it would be an appropriate time to consult with a physician. Other warning signs include a mole, even if smaller than a pencil eraser, that is different from the others and begins to crust over, bleed, itch, or become inflamed. The changes may indicate developing melanomas. The matter can become clinically complicated because mole removal depends on which types of cancer, if any, come into suspicion.

A recent and novel method of melanoma detection is the "ugly duckling sign" It is simple, easy to teach, and highly effective in detecting melanoma. Simply, correlation of common characteristics of a person's skin lesion is made. Lesions which greatly deviate from the common characteristics are labeled as an "ugly duckling", and further professional exam is required. The "little red riding hood sign", suggests that individuals with fair skin and light colored hair might have difficult-to-diagnose melanomas. Extra care and caution should be rendered when examining such individuals as they might have multiple melanomas and severely dysplastic nevi. A dermatoscope must be used to detect "ugly ducklings", as many melanomas in these individuals resemble non-melanomas or are considered to be "wolves in sheep clothing". These fair skinned individuals often have lightly pigmented or amelanotic melanomas which will not present easy-to-observe color changes and variation in colors. The borders of these amelanotic melanomas are often indistinct, making visual identification without a dermatoscope very difficult.

People with a personal or family history of skin cancer or of dysplastic nevus syndrome (multiple atypical moles) should see a dermatologist at least once a year to be sure they are not developing melanoma.

Nevi are typically diagnosed clinically with the naked eye or using dermatoscopy. More advanced imaging tests are available for distinguishing melanocytic nevi from melanoma, including computerized dermoscopy and image analysis. The management of nevi depends on the type of nevus and the degree of diagnostic uncertainty. Some nevi are known to be benign, and may simply be monitored over time. Others may warrant more thorough examination and biopsy for histopathological examination (looking at a sample of skin under a microscope to detect unique cellular features). For example, a clinician may want to determine whether a pigmented nevus is a type of melanocytic nevus, dysplastic nevus, or melanoma as some of these skin lesions pose a risk for malignancy. The ABCDE criteria (asymmetry, border irregularity, color variegation, diameter > 6 mm, and evolution) are often used to distinguish nevi from melanomas in adults, while modified criteria (amelanosis, bleeding or bumps, uniform color, small diameter or de novo, and evolution) can be used when evaluating suspicious lesions in children. In addition to histopathological examination, some lesions may also warrant additional tests to aid in diagnosis, including special stains, immunohistochemistry, and electron microscopy. Typically; the nevi which exist since childhood are harmless

The management of a nevus depends on the specific diagnosis, however, the options for treatment generally include the following modalities:

Most birthmarks are harmless and do not require treatment. Pigmented marks can resolve on their own over time in some cases. Vascular birthmarks may require reduction or removal for cosmetic reasons. Treatments include administering oral or injected steroids, dermatological lasers to reduce size and/or color, or dermatologic surgery.

Diagnosis is made primarily through physical assessment of the skin, family history of Mongolian spots, and subjective data given by the care giver. No tests are currently available for diagnosing Mongolian spots.

Gardasil 6 is an HPV vaccine aimed at preventing cervical cancers and genital warts. Gardasil is designed to prevent infection with HPV types 16, 18, 6, and 11. HPV types 16 and 18 currently cause about 70% of cervical cancer cases, and also cause some vulvar, vaginal, penile and anal cancers. HPV types 6 and 11 are responsible for 90% of documented cases of genital warts.

Gardasil 9, approved in 2014 protects against HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58.

HPV vaccines do not currently protect against the virus strains responsible for plantar warts (verrucas).

Common warts have a characteristic appearance under the microscope. They have thickening of the stratum corneum (hyperkeratosis), thickening of the stratum spinosum (acanthosis), thickening of the stratum granulosum, rete ridge elongation, and large blood vessels at the dermoepidermal junction.

Port-wine stains, also known as nevus flammeus and sometimes mistaken for strawberry marks, are present at birth and range from a pale pink in color, to a deep wine-red. Irregular in appearance, they are usually quite large, and caused by a deficiency or absence in the nerve supply to blood vessels. This causes vasodilation, the dilation of blood vessels, causing blood to pool or collect in the affected area. Over time, port-wine stains may become thick or develop small ridges or bumps, and do not fade with age. Such birthmarks may have emotional or social repercussions. Port-wine stains occur in 0.3% of the population, equally among males and females. They frequently express unilaterally, i.e., on only one side, not crossing the midline of the body. Often on the face, marks on the upper eyelid or forehead may be indicative of a condition called Sturge-Weber syndrome. Additionally, port-wine stains in these locations may be associated with glaucoma and seizures.

Mongolian spots usually resolve by early childhood and hence no treatment is generally needed if they are located in the sacral area. However, sometimes it may be required for extra sacral lesions to have surgical correction. Q-switched alexandrite lasers have been used for treatment. Good results are obtained if treatment is initiated before the age of 20 years. In a study done by the University of Tokyo, the effectiveness of the Q-switched alexandrite laser in treating Mongolian spots was evaluated. A retrospective study was done from April 2003 to September 2011. 16 patients, aged 14-55, were treated with Q-switched alexandrite laser. A good therapeutic outcome was achieved on the whole group, however two patients with sacral Mongolian spots suffered from inflammatory hyperpigmentation, and two patients got post inflammatory hypopigmentation after seven sessions of laser treatment.

Warty dyskeratoma, also known as an Isolated dyskeratosis follicularis, is a benign epidermal proliferation with distinctive histologic findings that may mimic invasive squamous cell carcinoma and commonly manifests as an umbilicated (Having a central mark or depression resembling a navel) lesion with a keratotic plug, WD have some histopathologic similarities to viral warts but it's not caused by HPV and the majority of these lesions display overall histopathologic features consistent with a follicular adnexal neoplasm. usually limited to the head, neck, scalp or face and vulva. Lesions are generally and sporadic and may be associated with a follicular unit. Oral involvement, particularly the hard palate, and genital involvement have been reported. it can also be thought of as one of the manifestations of focal acantholytic dyskeratosis, an epidermal reaction pattern that can be seen in several disorders, including Darier's disease and Grover's disease. But the main Difference between Darier disease and Warty dyskeratoma, is that Darier disease inherited dermatosis (autosomal dominant) consisting of multiple keratotic papules on the face, trunk, and extremities, while WD occurs as an isolated, noninherited, single keratotic nodule mainly confined to the head and neck as mentioned earlier.

Warty dyskeratoma must be differentiated from vulvar dysplasia, Bowenoid papulosis, squamous carcinoma, condyloma, and other viral-induced squamous lesions.

Treatment for fiddler’s neck is unnecessary if it is painless and shows minimal swelling, particularly since minor cases are taken as a mark of pride. But fiddler’s neck may lead to worse disorders. The primary methods of treatment involve adjustments to playing of the instrument:

- good hygiene for the affected area and for the instrument

- use of a clean cotton cloth that is changed frequently

- use of a shoulder rest to reduce pressure below the jaw

- a suitable chin rest, especially one carved or molded for the individual

- Covering or changing potentially allergenic materials on the instrument.

- shifting the chin rest to the center of the body over the tailpiece

- smoothing coarse surfaces to reduce abrasion

- for males, growing a beard to avoid folliculitis

Surgery is necessary for sialolithiasis, parotid tumors, and cysts. Cervical lymph nodes that are larger than 1 cm must be biopsied. Connective tissue can be removed by excision when a non-inflamed mass is large, and there is generally little recurrence. Infections should be treated conservatively, and causative species should be identified through smear and culture for appropriate antibiotic selection. Reduction of playing time may be helpful for cases without inflammation, but in 30% of cases this did not improve the symptoms.

Fiddler’s neck does not usually form unless the musician is practicing or playing for more than a few hours each day, and only seems to develop after a few years of serious playing. Thus, when not infected or otherwise problematic, fiddler’s neck may be known as a benign practice mark and may be worn proudly as an indication of long hours of practice. Blum & Ritter (1990) found that 62% of 523 professional violinists and violists in West Germany experienced fiddler’s neck, with the percentage among violists being higher (67%) than among violinists (59%). Viola players are believed to be more predisposed to developing fiddler’s neck than violinists because the viola is larger and heavier, but this has not been empirically confirmed.

The development of fiddler’s neck does not depend on preexisting skin problems, and Blum & Ritter find that only 23% of men and 14% of women in their study reported cutaneous disorders in other parts of the face (mainly acne and eczema) that were independent of playing the violin or viola. Fiddler’s neck may exacerbate existing acne, but acne may also be limited solely to the lesion and not appear elsewhere. Nonetheless, musicians with underlying dermatologic diseases like acne and eczema are more endangered by fiddler’s neck than others. Males may develop folliculitis or boils due to involvement of beard hair.

In longstanding scarred lesions, squamous cell carcinoma can develop.

On diascopy, it shows characteristic "apple-jelly" color. Biopsy will reveal tuberculoid granuloma with few bacilli. Mantoux test is positive.

Phakomatoses are inconsistently defined, and there is a lack of consensus about what conditions are included in this category.

Conditions included are:

- Ataxia telangiectasia

- Incontinentia pigmenti

- Neurofibromatosis

- Nevoid basal cell carcinoma syndrome

- Sturge-Weber syndrome

- Tuberous sclerosis

- Wyburn-Mason syndrome (Bonnet–Dechaume–Blanc syndrome)

- von Hippel-Lindau disease

Phakomatoses refers to a group of neuro-oculo-cutaneous syndromes or neurocutaneous disorders involving structures arising from the embryonic ectoderm. These multisystem disorders involve the ectodermal structures like central nervous system, skin and eyes. The lesions have a variable severity. However, it has been subsequently noted that mesodermal and endodermal tissues too are involved.

A number of genetic and acquired diseases come in this category and may affect one or more of these tissues. However, in some conditions, such as von Hippel-Lindau disease, ectodermal presentation is minimal.

Treatment is predominantly preventive. Avoidance of topical phenols and diets low in tyrosine may help. Replacement and repair of damaged tissue is also possible.

Using non-oily cleansers and mild soap may not cause as much irritation to the skin as regular soap. Blackheads can be removed across an area with commercially available pore-cleansing strips or the more aggressive cyanoacrylate method used by dermatologists.

Squeezing blackheads and whiteheads can remove them, but it can also damage the skin. Doing so increases the risk of causing or transmitting infection and scarring, as well as potentially pushing any infection deeper into the skin. Comedo extractors are used with careful hygiene in beauty salons and by dermatologists, usually after using steam or warm water.

Complementary medicine options for acne in general have not been shown to be effective in trials. These include aloe vera, pyridoxine (vitamin B6), fruit-derived acids, kampo (Japanese herbal medicine), ayurvedic herbal treatments and acupuncture.

Some acne treatments target infection specifically, but there are treatments that are aimed at the formation of comedones as well. Others remove the dead layers of the skin and may help clear blocked pores.

Dermatologists can often extract open comedones with minimal skin trauma, but closed comedones are more difficult. Laser treatment for acne might reduce comedones, but dermabrasion and laser therapy have also been known to cause scarring.

Macrocomedones (1 mm or larger) can be removed by a dermatologist using surgical instruments or cauterized with a device that uses light. The acne drug isotretinoin can cause severe flare-ups of macrocomedones, so dermatologists recommend removal before starting the drug and during treatment.

Some research suggests that the common acne medications, retinoids and azelaic acid, are beneficial and do not cause increased pigmentation of the skin.

Hydroquinone-induced exogenous ochronosis is an avoidable dermatosis that is exceedingly difficult to treat.

However, some studies show that treatment may be possible with a Q-switched alexandrite (755 nm) laser.

It is recommended that individuals with this disorder stop using hydroquinone-containing compounds. It is important to be aware of this as dermatologists may think the symptoms a patient is exhibiting are a melasma, and prescribe a hydroquinone-containing cream.

Diagnosis is achieved by examining the structure of the chromosomes through karyotyping; while once born, one can do the following to ascertain a diagnosis of the condition:

- MRI

- EEG

Ring chromosome 14 syndrome is extremely rare, the true rate of occurrence is unknown (as it is "less than" 1 per 1,000,000), but there are at least 50 documented cases in the literature.

Placing the cat's water in a shallow dish may prevent the chin from absorbing the bacteria in the water while the cat is drinking. If the cat is allergic to plastics or dyes, using a stainless-steel or glass dish is recommended . Cats may also have food allergies that make the development of acne more likely, so that switching kibble, or changing to a hydrolysed diet may be effective. Maintaining good hygiene and grooming habits make the development of feline acne less likely. Washing and exfoliating the chin with a gentle benzoyl-peroxide solution also may be preventive of further outbreaks.

Carbon stains are a skin condition characterized by a discoloration of the skin from embedded carbon, usually occurring in children from accidents with firearms or firecrackers, or from a puncture wound by a pencil, which may leave a permanent black mark of embedded graphite, easily mistaken for metastatic melanoma.