CHAPTER 6: The Skin, Hair, and Nails



In this edition, you will find a helpful new approach to examining the skin, hair, and nails and many new tables and photographs. This approach features careful history taking; thorough inspection and palpation of benign and suspicious lesions to better detect the three major skin cancers—basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma; focused techniques for assessing changes in the hair and nails; accurate use of terminology to describe your findings; and visual familiarity with important common benign and malignant skin conditions. Updated information on skin cancer prevention and screening is found in the section on Health Promotion and Counseling.

Anatomy and Physiology

The skin keeps the body in homeostasis despite daily assaults from the environment. It retains body fluids while protecting underlying tissues from microorganisms, harmful substances, and radiation. It modulates body temperature and synthesizes vitamin D. Hair, nails, and sebaceous and sweat glands are considered appendages of the skin. The skin and its appendages undergo many changes during aging.

Turn to Chapter 20, The Older Adult, pp. 955–1008, to review skin changes with aging.


The skin is the heaviest single organ of the body, accounting for approximately 16% of body weight and covering an area of roughly 1.2 to 2.3/m2. It contains three layers: the epidermis, the dermis, and the subcutaneous tissues.

The most superficial layer, the epidermis, is thin avascular keratinized epithelium consisting of two layers: an outer horny stratum corneum of dead keratinized cells; and an inner cellular layer, the stratum basale and the stratum spinosum, also known as the malpighian layer, where both melanin and keratin are formed. Migration from the inner to the outer layer takes approximately 1 month.

The epidermis depends on the underlying vascularized dermis for nutrition. The dermis is a dense layer of interconnecting collagen and elastic fibers containing sebaceous glands, sweat glands, hair follicles, and most of the terminals of the cutaneous nerves (Fig. 6-1). Inferiorly, the dermis merges with subcutaneous fatty tissue, or adipose tissue.

FIGURE 6-1 Anatomy of the skin.

Anatomy of the skin.

Normal skin color depends on the amount and type of melanin, but is also influenced by underlying vascular structures, changing hemodynamics, and changes in carotene and bilirubin. The amount of melanin, a brownish pigment, is genetically determined and increased by exposure to sunlight. Hemoglobin in the red blood cells transports oxygen in the form of oxyhemoglobin, a bright red pigment in the arteries and capillaries that causes reddening of the skin.

After passing through the capillary bed and releasing oxygen to the tissues, the darker bluer pigment of deoxyhemoglobin circulates in the veins. The scattering of light through the turbid superficial layers of the skin or blood vessels also makes the veins look bluer and less red than circulating venous blood.

Pallor indicates anemia.

Cyanosis, a blue color, can indicate decreased oxygen in the blood or decreased blood flow in response to a cold environment

Carotene, a yellow pigment, is found in the subcutaneous fat and heavily keratinized areas such as the palms and soles. Bilirubin, a yellow-brown pigment, arises from the breakdown of heme in the red blood cells.

Jaundice, or yellowing of the skin, results from increased bilirubin.


Adults have two types of hair: vellus hair, which is short, fine, inconspicuous, and relatively unpigmented; and terminal hair, which is coarser, thicker, more conspicuous, and usually pigmented. Scalp hair and eyebrows are examples of terminal hair.


Nails protect the distal ends of the fingers and toes. The firm rectangular and usually curving nail plate gets its pink color from the vascular nail bed to which the plate is firmly attached (Figs. 6-2 and 6-3). Note the whitish moon, or lunula, and the free edge of the nail plate. Roughly one-fourth of the nail plate, the nail root, is covered by the proximal nail fold. The cuticle extends from the fold and, functioning as a seal, protects the space between the fold and the plate from external moisture. Lateral nail folds cover the sides of the nail plate. Note that the angle between the proximal nail fold and nail plate is normally less than 180°.

FIGURE 6-2 Anatomy of the fingernail.

Anatomy of the fingernail.

FIGURE 6-3 Cross-section of fingernail.

Cross-section of fingernail.

Fingernails grow approximately 0.1 mm daily; toenails grow more slowly.

Sebaceous Glands and Sweat Glands

Sebaceous glands produce a fatty substance secreted onto the skin surface through the hair follicles. These glands are present on all skin surfaces except the palms and soles.

Sweat glands are of two types: eccrine and apocrine. The eccrine glands are widely distributed, open directly onto the skin surface, and by their sweat production help to control body temperature. In contrast, the apocrine glands are found chiefly in the axillary and genital regions and usually open into hair follicles. Bacterial decomposition of apocrine sweat is responsible for adult body odor.

The Health History

Common or Concerning Symptoms

  • Growths
  • Rashes
  • Hair loss or nail changes


Start by asking if the patient is concerned about any new growths or rashes: “Have you noticed any changes in your skin? … your hair? … your nails?” “Have you had any rashes? … sores? … lumps? … itching?” If the patient reports a new growth, it is important to pursue the patient’s personal and family history of skin cancer.

Note the type, location, and date of any past skin cancer and ask about regular self-skin examination and use of sunscreen. Also ask “Has anyone in your family had a skin cancer removed? If so, who? Do you know what type of skin cancer—basal cell carcinoma, squamous cell carcinoma, or melanoma?” Document the response even if the patient does not know which type and counsel the patient about skin cancer prevention.

See discussion of prevention in Health Promotion and Counseling section, pp. 176–180.


For complaints of rash, ask about itching, the most important symptom when assessing rashes. Does itching precede the rash or follow the rash? For itchy rashes, ask about seasonal allergies with itching and watery eyes, asthma, and atopic dermatitis, often accompanied by rash on the inside of the elbows and knees in childhood. Can the patient sleep all night or does itching wake up the patient? For rashes, it is important to find out what type of moisturizer or over-the-counter products have been applied.

Causes of generalized itching, without apparent rash, include dry skin; pregnancy; uremia; jaundice; lymphomas and leukemia; drug reactions; and, less commonly, polycythemia vera and thyroid disease.

Also, ask about dry skin, which can cause itching and rash, especially in children with atopic dermatitis and older adults, due to loss of the natural moisture barrier in the epidermis.

Encourage use of moisturizers to replace the lost moisture barrier. Some recommended brands even include sunscreen.1,2

Hair Loss or Nail Changes

Patients often report hair loss or nail changes spontaneously. For hair loss, ask if there is hair thinning or hair shedding and, if so, where. If shedding, does the hair come out at the roots or break along the hair shafts? Ask about hair care practices like frequency of shampooing and use of dyes, chemical relaxers, or heating appliances.

See Table 6-11, pp. 209–210, for normal patterns of hair loss in men and women and counsel affected patients appropriately. Be familiar with common nail changes such as onychomycosis, habit tic deformity, and melanonychia, shown in Table 6-12, pp. 211–212.

The most common causes of diffuse hair thinning are male and female pattern baldness

Hair shedding at the roots is common in telogen affluvium and alopecia areata. Hair breaks along the shaft suggest damage from hair care or tinea capitis.

Health Promotion and Counseling: Evidence and Recommendations

Important Topics for Health Promotion and Counseling

  • Skin cancer prevention
  • Skin cancer screening

Skin Cancer Prevention

Clinicians play a vital role in educating patients about skin cancer prevention. Skin cancers are the most common cancers in the United States, affecting an estimated one in five Americans during their lifetime.[3] They are caused by a combination of genetic predisposition and ultraviolet radiation exposure. Fair-skinned individuals are at highest risk. The most common skin cancer is basal cell carcinoma (BCC), followed by squamous cell carcinoma (SCC), and melanoma.

For discussion and examples of types of skin cancers, turn to the tables on pp. 197–203.


Although it is the least common skin cancer, melanoma is the most lethal due to its high rate of metastasis and high mortality at advanced stages, causing over 70% of skin cancer deaths.[4] The incidence of melanoma has more than doubled in the past three decades, the most rapid increase of any cancer.[5] Melanoma is now the fifth most frequently diagnosed cancer in men and the seventh most frequently diagnosed in women. In the United States in 2014, the estimated lifetime risk was 1 in 48 for whites (2%), 1 in 200 for Hispanics, and 1 in 1,000 for African Americans.[6]

Ask patients about the melanoma risk factors listed below, and use of the Melanoma Risk Assessment Tool developed by the National Cancer Institute, available at This tool assesses an individual’s 5-year risk of developing melanoma based on geographic location, gender, race, age, history of blistering sunburns, complexion, number and size of moles, freckling, and sun damage. It is applicable up to age 70 years, but is not intended for patients with a family history of melanoma.

Risk Factors for Melanoma

  • Personal or family history of previous melanoma4,7–9
  • ?50 common moles
  • Atypical or large moles, especially if dysplastic
  • Red or light hair
  • Solar lentigines (acquired brown macules on sun-exposed areas)
  • Freckles (inherited brown macules)
  • Ultraviolet radiation from heavy sun exposure, sunlamps, or tanning booths
  • Light eye or skin color, especially skin that freckles or burns easily
  • Severe blistering sunburns in childhood
  • Immunosuppression from human immunodeficiency virus (HIV) or from chemotherapy
  • Personal history of nonmelanoma skin cancer

Avoiding Ultraviolet Radiation and Tanning Beds

Increasing lifetime sun exposure correlates directly with increasing risk of skin cancer. Intermittent sun exposure appears to be more harmful than chronic exposure.[9] The best defense against skin cancers is to avoid ultraviolet radiation exposure by limiting time in the sun, avoiding midday sun, using sunscreen, and wearing sun-protective clothing with long sleeves and hats with wide brims. Advise patients to avoid indoor tanning, especially children, teens, and young adults. Use of indoor tanning beds, especially before age 35 years, increases risk of melanoma by as much as 75%.

Signs of chronic sun damage include numerous solar lentigines on the shoulders and upper back, many melanocytic nevi, solar elastosis (yellow, thickened skin with bumps, wrinkles, or furrowing), cutis rhomboidalis nuchae (leathery thickened skin on the posterior neck), and actinic purpura. See Table 6-9, Signs of Sun Damage, on p. 206.

In 2009, the International Agency for Research on Cancer classified ultraviolet-emitting tanning devices as “carcinogenic to humans.”[10] Options for tanning include self-tanning products or sprays in conjunction with sunscreen. Targeted patient messages in primary care practices have been shown to amplify these sun-protective behaviors.[11],[12]

The U.S. Preventive Services Task Force (USPSTF) has made a grade B recommendation supporting behavioral counseling through minimizing ultraviolet radiation exposure in fair-skinned children, adolescents, and young adults aged 10 to 24 years and cites insufficient evidence, grade I, for counseling adults older than 24 years, but noted no harms associated with counseling.[13]

Regular Use of Sunscreen Prevents Skin Cancer

There are many myths about sunscreen. A landmark study in 2011 demonstrated that the regular use of sunscreen decreases the incidence of melanoma.[14] This well-designed study showed that when clinicians strongly encouraged use of sunscreen, patients were more likely to use it regularly and melanoma incidence declined.

Advise patients to use at least sun protective factor (SPF) 30 and broad-spectrum protection (Fig. 6-4). For water exposure, patients should use water-resistant sunscreens. New U.S. Food and Drug Administration labeling guidelines in 2011 make it easy to see these features on all bottles of sunscreen. Free information about protection and proper use of sunscreen are available from the AAD and the Skin Cancer Foundation.[15],[16]

FIGURE 6-4 Advise use of broad spectrum sunscreen with SPF 30.

Advise use of broad spectrum sunscreen with SPF 30.

Skin Cancer Screening

Although the USPSTF found insufficient evidence (grade I) to recommend routine skin cancer screening by primary care physicians, it does advise clinicians to “remain alert for skin lesions with malignant features” during routine physical examinations and reference the ABCDE criteria.[17],[18] The American Cancer Society (ACS) and the AAD recommend full-body examinations for patients over age 50 years or at high risk, because melanoma can appear in any location.[15],[19]

High-risk patients are those with a personal or family history of multiple or dysplastic nevi or previous melanoma. Patients who have a clinical skin examination within the 3 years prior to a melanoma diagnosis have thinner melanomas than those who did not have a clinical skin examination.[20] Both new and changing nevi should be closely examined, as at least half of melanomas arise de novo from isolated melanocytes rather than pre-existing nevi. Also consider “opportunistic screening” as part of the complete physical examination for patients with significant sun exposure and patients over age 50 years without prior skin examination or who live alone.

Since the USPSTF review, an important German study of over 350,000 patients reported that full-body primary care screening with dermatology referrals for concerning lesions reduced melanoma mortality by more than 47%.[21] Survival from melanoma strongly correlates with tumor thickness. Two further studies demonstrate that patients receiving skin examinations are more likely to have thinner melanomas.[20],[22]

Detecting melanoma requires practice and knowledge of how benign nevi change over time, often going from flat to raised or acquiring additional brown pigment. Studies have shown that even limited clinician training makes a difference in detection: patients of primary care providers who spent 1.5 hours completing an online tutorial improved diagnostic accuracy. Similar studies show such training results in thinner melanomas than patients of providers without such training.[23]–[26]

Turn to Tables 6-4 through 6-6 on pp. 197–203 showing rough, pink, and brown nevi and their mimics.

Screening for Melanoma: The ABCDEs

Clinicians should apply the ABCE-EFG method when screening moles for melanoma (this does not apply for non-melanocytic lesions like seborrheic keratoses) . The sensitivity of this tool for detecting melanoma ranges from 43% to 97%, and specificity ranges from 36% to 100%; diagnostic accuracy depends on how many criteria are used to define abnormality.[27] If two or more of these features are present, biopsy should be considered. The most sensitive is E, for evolution or change. Pay close attention to nevi that have changed rapidly based on objective evidence.

Review the ABCDE-EFG rule and photographs in Table 6-6, pp. 200–203, which provide additional helpful identifiers and comparisons of benign brown lesions with melanoma.

The ABCDE Rule

The ABCDE method has been used for many years to teach clinicians and patients about features suspicious for melanoma. If two or more of these are present, risk of melanoma increases and biopsy should be considered. Some have suggested adding EFG to help detect aggressive nodular melanomas.

Melanoma Benign Nevus
Asymmetry Of one side of mole compared to the other Image not available Image not available
Border irregularity
Especially if ragged, notched, or blurred
Image not available Image not available
Color variations More than two colors, especially blue-black, white (loss of pigment due to regression), or red (inflammatory reaction to abnormal cells) Image not available Image not available
Diameter >6 mm Approximately the size of a pencil eraser Image not available Image not available
Evolving Or changing rapidly in size, symptoms, or morphology Image not available Image not available
  • Elevated
  • Firm to palpation
  •  Growing progressively over several weeks

With the exception of a homogenous blue color in a blue nevus, blue or black color within a larger pigmented lesion is especially concerning for melanoma.

Early melanomas may be <6 mm, and many benign lesions are >6 mm.

Evolution, or change, is the most sensitive of these criteria. A reliable history of change may prompt biopsy of a benign-appearing lesion.

Patient Screening: The Self Skin Examination

The AAD and the ACS recommend regular self-skin examination based on expert opinion.[15],[28] Instruct patients with risk factors for skin cancer and melanoma, especially those with a history of high sun exposure, prior or family history of melanoma, and ?50 moles or >5 to 10 atypical moles, to perform regular self-skin examinations.

Patients who examine their skin regularly are more likely to have thinner melanomas, if detected.[24],[29] Teach patients about the appearance of different skin cancers, making use of the excellent resources available on the internet.[15]

See Patient Instructions for Self Skin Examination, pp. 187–188.

Approximately half of melanomas are initially detected by patients or their partners.