Scaly upper layer
sweat glands, sebaceous glands,
and lymph vessels, and sensory receptors
for pressure, temperature, and pain.
skin allergy Irritation of the skin follow-
ing contact with a specific substance that
provokes an inappropriate or exagger-
ated reaction from the
There are 2 main types of allergic skin
reaction. In contact allergic
red, itchy patches develop a few hours
days after contact with the allergen.
, red, raised areas
appear a few minutes after skin contact.
In some cases,
are needed, to
identify the allergen, for contact with it to
be minimized. (See also atopic
skin biopsy Removal of a portion of skin
for laboratory analysis in order to diag-
nose a skin disorder.
skin cancer A malignant tumour in the
skin. Basal cell carcinoma, squamous cell
common forms related to long-term
exposure to sunlight.
rare disorder that can become cancer-
ous, may also be related to sun exposure.
Less common types include
ease of the nipple
is a type usually found
in people with
. Most skin cancers
can be cured if treated early.
skin, disorders of the
The skin is vul-
nerable to various disorders, including
that may be viral (such as
), bacterial (for example,
or fungal (such as
, which causes
due to vitamin
deficiency or the side effects of drugs;
and tumours, both noncancerous and
is common in adoles-
cents and is partly related to the action
. Inflammation of
the skin occurs in
. The skin is also vulner-
able to injuries such as
, cuts, and
skin flap A surgical technique in which
a section of
and underlying tissue,
sometimes including muscle, is moved
to cover an area from which skin and tis-
sue have been lost or damaged by injury,
disease, or surgery. Unlike a
skin flap retains its blood supply, either
by remaining attached to the donor site
or through reattachment to blood vessels
at the recipient site by
skin flaps adhere well even where there
is extensive loss of deep tissue.
skin graft A technique used to repair
areas of lost or damaged
too large to heal naturally, that are slow