S

scabies A contagious parasitic infestation with
the SKINmite Sarcoptes scabeithat typically causes
intense itching (PRURITUS) and visible bites or irri-
tation to the skin. The bites create small, reddened
papules (bumps) and often a RASHon the sur-
rounding skin that is the burrows the mites make
to lay their eggs. The most common sites for sca-
bies 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 scrap-
ings of the papules or rash. Microscopic examina-
tion of the scrapings often reveals eggs or fecal
matter from the mites. Applying a lotion that con-
tains 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 alsoBACTERIA; INFECTION; PAPULE; PARASITES;
PEDICULOSIS.

scale A SKIN LESIONin 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

drop from the skin, often as visible flakes such as

characterizeDANDRUFF.

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 hyper-

trophic 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

LESIONthat 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 HAIRfollicles,

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.

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