C h a p t e r 4 5
Structure and Function of the Integumentum
1151
skin, reducing transepidermal water loss, and restoring
the lipid barrier’s ability to attract, hold, and redistrib-
ute water. Moisturizing agents can be classified as emol-
lients, humectants, and occlusives.
Emollients
are fatty
acid–containing lotions that replenish the oils on the
skin surface, but usually do not leave a residue on the
skin. They have a short duration of action and need to
be applied frequently.
Humectants
are the additives in
lotions, such as
α
-hydroxy acids and urea, that draw out
water from the deeper skin layers and hold it on the skin
surface. However, the water that is drawn to the skin
is transepidermal water, not atmospheric water; thus,
continued evaporation from the skin can actually exac-
erbate dryness.
α
-Hydroxy acids are derived from fruits,
hence the abundance of fruit additives in over-the-coun-
ter shampoos and lotions. Urea is a nitrogenous sub-
stance that has been quite effective in reducing xerosis
when combined with lotions. It is a humectant at lower
concentrations (10%), but in higher concentrations
(20% to 30%) it is mildly keratolytic. Clinical trials of
urea have indicated its utility compared with ammo-
nium lactate (lactic acid) lotion and glycerin.
Occlusives
are thick creams that contain petroleum or some other
moisture-proof material. They prevent water loss from
the skin. They are the most effective agents for relieving
skin dryness, but because of their greasiness and lack of
cosmetic appeal, some people do not wish to use them.
Lotion or cream additives include corticosteroids or
mild anesthetics, such as camphor, menthol, lidocaine,
or benzocaine. These agents work by suppressing itch-
ing while moisturizing the skin. Using room humidifi-
ers and keeping room temperatures as low as possible
to prevent water loss from the skin also may be help-
ful. Soaps with moisturizers may be helpful. Glycerine
soaps, although popular and visually appealing, are
drying and can exacerbate the symptoms.
Variations in Dark-Skinned People
Some skin disorders common to people of African,
Hispanic, or East Indian descent are not commonly
found in those of European descent. Other skin disor-
ders, such as skin cancers, affect light-skinned persons
more commonly than dark-skinned persons. Because of
these differences, serious skin disorders may be over-
looked, and normal variations in darker skin may be
mistaken for anomalies.
As noted earlier, skin color is determined by the mela-
nin produced by the melanocytes. Although the number
of melanosomes in dark and white skin is the same, black
skin produces more melanin, and more quickly, than white
skin. Because of their skin color, dark-skinned persons are
better protected against skin cancer, premature wrinkling,
and aging of the skin that occurs with sun exposure.
A condition common in people with dark skin is too
much or too little color. Areas of the skin may darken
after injury, such as a cut or scrape, or after disease con-
ditions such as acne. These darkened areas may take
many months or years to fade. Dry or “ashy” skin is also
a common problem for people with dark skin. It often
is uncomfortable, and it also is easily noticed because it
gives the skin an ashen or grayish appearance. Although
using a moisturizer may help relieve the discomfort, it
may cause a worsening of acne in predisposed persons.
Normal variations in skin structure and skin tones often
make evaluation of dark skin difficult. The darker pigmen-
tation can make skin pallor, cyanosis, and erythema more
difficult to observe. Therefore, verbal histories must be
relied on to assess skin changes. The verbal history should
include the client’s description of her or his normal skin
tones. Changes in skin color, in particular hypopigmenta-
tion and hyperpigmentation, often accompany disorders
of dark skin and are very important signs to observe when
diagnosing skin conditions. Common variations in dark
skin and nails are described in Table 45-1.
SUMMARY CONCEPTS
■■
Skin lesions are a loss of skin integrity and rashes
are temporary skin eruptions.They are the most
common manifestations of both skin and many
systemic diseases.They vary in size and color;
they can be flat (macule or patch), palpable
(papule, plaque, or nodule), or fluid-filled
elevations (vesicle or bullae).
■■
Erosions involve a loss of the superficial
epidermis, and an ulcer a loss of the epidermis
and papillary layer of dermis.
Developed from information in RosenT, Martin S. Atlas of Black
Dermatology. Boston, MA: Little, Brown; 1981.
TABLE 45-1
Common Normal Variations
in Dark Skin
Variation
Appearance
Futcher (Voigt)
line
Demarcation between darkly
pigmented and lightly pigmented
skin in upper arm; follows spinal
nerve distribution; common in black
and Japanese populations
Midline hypo-
pigmentation
Line or band of hypopigmentation
over the sternum, dark or faint,
lessens with age; common in Latin
American and black populations
Nail
pigmentation
Linear dark bands down nails or
diffuse nail pigmentation; brown,
blue, or blue-black
Oral
pigmentation
Blue to blue-gray pigmentation of oral
mucosa; gingivae also affected
Palmar changes
Hyperpigmented creases, small
hyperkeratotic papules, and tiny pits
in creases
Plantar changes
Hyperpigmented macules; can be
multiple with patchy distribution,
irregular borders, and variance in
color
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