raasm007

Causes

Because skin is so closely associated with beauty and
sensuality, it's easy to forget the crucial role it
plays in maintaining health. Although only about a
tenth of an inch thick, your skin performs a number of
essential functions, including protecting you from
viruses, bacteria and environmental assaults,
maintaining adequate hydration, and helping regulate
body temperature.

Your skin consists of three layers:

Epidermis. This outer layer, no thicker than a sheet
of paper, both shields you from the world and presents
you to it.
Dermis. This thick middle layer makes up most of your
skin. It contains collagen and elastin — fibers that
give your skin strength, structure and elasticity.
Subcutaneous layer. This layer, which is mainly fat,
is the source of your skin's nerves and blood vessels
as well as the roots of your hair follicles, oil
glands and sweat glands.
Basal cells make up the base of the epidermis. They
divide to form squamous cells that produce keratin, a
hard protein that protects your skin from harmful
substances and infection. As the basal cells divide,
they push new squamous cells toward the surface of the
epidermis, where they eventually shrink, flatten and
die. These dead cells make up the stratum corneum, the
outermost portion of the epidermis. Stratum corneum
cells flake off every day and are continuously
replaced by more cells. It usually takes about a month
for skin cells to move from the basal layer to the
stratum corneum.

But the stratum corneum is far more than a place where
cells go to die. Instead, it's a dynamic structure
that affects not only your skin's appearance but also
its health. That's because the part of the stratum
corneum between the cells is composed mainly of fats
(lipids) such as ceramides, cholesterol and fatty
acids. These fats form a strong, protective barrier
that preserves the moisture in your body. Strip away
the barrier and your skin cells lose the water they
need to stay healthy and supple. Although many of the
characteristics of dry skin are subjective —
roughness, lack of radiance, tightness — scientists
define dry skin based on specific, measurable changes
in water and lipids in the stratum corneum.

A healthy stratum corneum is about 30 percent water,
giving your skin resilience and elasticity. Most of
the water is in the interior of the stratum corneum —
in the outer layers, the water level depends on the
amount of humidity in the air. The drier the air, the
drier the outermost layer of skin.
Environmental factors
Most cases of ordinary dry skin are due to
environmental causes, such as:

Weather. In general, your skin is driest in winter
when temperatures and humidity levels plummet. Winter
conditions also tend to make existing skin conditions
worse. But the reverse may be true if you live in
desert regions, where summer temperatures can top 110
F and humidity levels sink to 10 percent or less.
Central heating and air conditioning. These may be
technological marvels, but they're dermatological
disasters. Central air and heating, wood burning
stoves, space heaters and fireplaces all draw moisture
out of the air and out of your skin.
Too much 'cleanliness is next to godliness.' When it
comes to your skin, water is a double-edged sword.
Inside your skin, it keeps the cells plump and moist,
but it has the opposite effect when you're immersed in
it. Frequent showering or bathing, especially if you
like your showers hot and your baths long, breaks down
the lipid barriers in your skin. So does frequent
swimming, particularly in heavily chlorinated pools.
Harsh soaps and detergents. Many popular soaps and
detergents strip lipids and water from your skin.
Products containing fragrances and lauryl sulfates are
harsher and more irritating than unscented products
with sarcosinates, sulfosuccinates and
cocoamphodiacetates. Deodorant and antibacterial soaps
are usually the most damaging, as are many shampoos,
which can dry out your scalp.
Other factors
Certain diseases, metabolic problems and nutritional
deficiencies can significantly alter the function and
appearance of your skin:

Ichthyosis. This group of inherited disorders occurs
either because skin cells don't shed quickly enough or
because they shed too quickly. Although the different
forms of ichthyosis vary in their pattern of
inheritance, the genes in which mutations occur, the
age when they first appear and their physical
manifestations, all cause dry, rough, scaly skin. In
rare cases, ichthyosis may be acquired in adulthood
rather than inherited, usually as a result of a
systemic disease such as cancer or HIV infection.
Certain drugs also may cause acquired ichthyosis.
Asteatotic eczema. Several factors can contribute to
asteatotic eczema, including certain neurologic
disorders and exposure to harsh soaps, to chemicals or
to cold, dry air. Older adults are especially prone to
the condition because their skin may be compromised by
dehydration, malnutrition or aging.
Psoriasis. This skin condition is marked by a rapid
buildup of rough, dry, dead skin cells that form thick
scales. Normally, it takes about a month for new skin
cells to move from the lowest layer of your skin,
where they first form, to the stratum corneum, but in
psoriasis the life cycle of skin cells speeds up.
Although a defective gene for the disorder hasn't been
discovered, most scientists believe psoriasis is an
inherited condition that may be triggered or
exacerbated by infections, skin injuries, a reaction
to a vaccine or medication, stress, alcohol or
long-time exposure to the sun or chemicals.
Thyroid disorders. Hypothyroidism, a condition that
occurs when your thyroid produces too few hormones,
reduces the activity of your sweat and oil glands,
leading to rough, dry skin.
Alcohol and drugs. Alcohol and caffeine can visibly
dry your skin. Prescription drugs such as diuretics,
antihistamines and isotretinoin (Accutane) also have a
drying effect.
Nutritional deficiencies. A long-term lack of
essential lipids, especially omega-3 fatty acids, can
affect the integrity of your skin. So can a deficiency
of the mineral zinc, which plays a key role in wound
healing and in the metabolism of fatty acids and
vitamin A.
Dehydration. Severe diarrhea and vomiting, a high
fever, profuse sweating during exercise or simply not
drinking enough liquids can cause your body to lose
more fluid than you take in. One of the first signs of
dehydration is skin that has lost its elasticity.

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