Encyclopedia of Health and Medicine

S
scabies A contagious parasitic infestation with
the SKIN mite Sarcoptes scabei that typically causes
intense itching (PRURITUS) and visible bites or irritation
to the skin. The bites create small, reddened
papules (bumps) and often a RASH on the surrounding
skin that is the burrows the mites make
to lay their eggs. The most common sites for scabies
are skinfold areas such as in the groin, under
the breasts and armpits, between the shoulders,
behind the knees, at the creases in the elbows,
and on the inner wrists. Itching typically becomes
intense at night. Aggressive scratching can cause
secondary bacterial infections of the skin to
develop. Scabies spreads through close physical
contact.
The doctor diagnoses scabies with skin scrapings
of the papules or rash. Microscopic examination
of the scrapings often reveals eggs or fecal
matter from the mites. Applying a lotion that contains
a pesticide such as permethrin, lindane, or
crotamiton will kill the mites, though the itching
may persist for a few days. All members of the
household should receive treatment. It is also
important to wash clothing, towels, and bed linens
in very hot (130ºF) water for at least 10 minutes
as a precaution to kill any mites these items might
be harboring, as mites can live outside the body
for up to 36 hours. Reinfestation may occur with
reexposure.
See also BACTERIA; INFECTION; PAPULE; PARASITES;
PEDICULOSIS.
scale A SKIN LESION in which keratinocytes clump
together instead of falling away from the skin,
adhering to the skin. Keratinocytes separated from
the epidermis are nearly translucent, often giving
scales a silver or white cast. When enough scales
accumulate, their weight causes them to finally
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drop from the skin, often as visible flakes such as
characterize DANDRUFF.
See also DERMATITIS; ICHTYOSIS; KERATINOCYTE;
PLAQUE, SKIN; PSORIASIS; SEBORRHEIC KERATOSIS.
scar A formation of fibrous tissue that remains
at the site of a healed wound. Though a scar will
not entirely match the surrounding tissue, most
scars heal to be barely noticeable.
Some scars become overgrown. A hypertrophic
scar is enlarged though does not extend beyond
the original wound site. Over time, most hypertrophic
scars retreat to become less noticeable. The
dermatologist may reduce a hypertrophic scar by
injecting it with an intralesional corticosteriod
medication or with pulsed dye laser treatments.
The success of such procedures depends on the
location and nature of the hypertrophic scar.
KELOID scars occur when the scar formation
process continues after the wound heals. The
keloid continues to grow, becoming a spongy
LESION that no longer has anything to do with
wound HEALING. Keloids can become quite large.
The dermatologist may remove keloids that are
continually irritated, such as by clothing, or that
are cosmetically undesirable. However, keloids
tend to recur.
See also PLASTIC SURGERY.
sebaceous glands The small glands that produce
sebum, a lipid-based, oily fluid that lubricates the
surface of the SKIN. Sebum is mostly the metabolic
waste that remains after fat cells break down.
Most sebaceous glands empty into HAIR follicles,
secreting sebum along the emerging hair shaft.
Some sebaceous glands exist independent of hair
follicles and secrete sebum directly to the skin’s
surface, such as those on the glans of the PENIS.