Date Posted: 01:37:23 11/15/04 Mon
How do Sunless Tanning products work?
Skin is made up of two main layers: the epidermis on the outside and
the dermis on the inside. Whether you are talking about sun tanning or
self-tanning, the epidermis is where the action occurs. The epidermis
is also made up of layers. The deepest layer of the epidermis, called
the stratum basale (basal layer), is affected during sun tanning. The
stratum corneum (horny layer) is the outermost layer of the epidermis
-- it is this layer that is affected by most sunless-tanning products.
There are several different kinds of sunless-tanning products available
today. People have been able to pour on a tan since 1960, when
Coppertone® came out with the first sunless-tanning product -- QT® or
Quick Tanning Lotion. If you are old enough to remember this, then you
are probably thinking of the incredibly orange hue this lotion
produced. Since then, there have been several advancements made on the
sunless-tanning front. These days, you can find tanning pills, sunless-
or self-tanners and bronzers. You can smooth, swipe or spray on a light
bronze glow or a deep, dark tan. Many of these products take 45 minutes
to one hour to start taking effect, and once you factor in drying time,
you could be looking at about three hours spent achieving that sun-free
tan.
The most effective products available are sunless- or
self-tanning lotions that contain dihydroxyacetone (DHA) as the active
ingredient (American Academy of Dermatology). DHA is a colourless sugar
that interacts with the dead cells located in the stratum corneum of
the epidermis. As the sugar interacts with the dead skin cells, a
colour change occurs. This change usually lasts about five to seven
days from the initial application. Every day, millions of dead skin cells are sloughed off or
worn away from the surface of your skin. In fact, every 35 to 45 days,
you have an entirely new epidermis. This is why tans from sunless- or
self-tanning lotions will gradually fade -- as the dead cells are worn
away, so is your tan. For this reason, most of these products suggest
that you reapply the sunless- or self-tanner about every three days to
maintain your "tan." Although gels, lotions or sprays that contain DHA are said
to be the most reliable and useful, there are dozens of other types of
products on the market. Tanning accelerators -- lotions or pills that
usually contain the amino acid tyrosine -- claim that they stimulate
and increase melanin formation, thereby accelerating the tanning
process. At this time, there is no scientific data available to support
these claims. Another sunless-tanning product is a tanning pill that
contains canthaxanthin, which is most commonly used as a colour
additive in certain foods. Although the FDA has approved the use of
canthaxanthin in food, it does not approve its use as a tanning agent.
When used as a colour additive, only very small amounts of
canthaxanthin are necessary. As a tanning agent, however, much larger
quantities are used. After canthaxanthin is consumed, it is deposited
all over your body, including in your skin, which turns an orange-brown
colour. These types of tanning pills have been linked to various side
effects, including hepatitis and canthaxanthin retinopathy, a condition
in which yellow deposits form in the retina of the eye. Another popular form of sunless tanning is the bronzer.
These powders and moisturizers, once applied, create a tan that can
easily be removed with soap and water. More like make-up, these
products tint or stain your skin only until they are washed off. It's important to remember that most of these products,
unless they contain an added sunscreen, will not protect you from the
sun's UVA and UVB rays. Even products that do contain a sunscreen won't
be of much help, since they lose their efficacy within hours of
application. So, if you're planning to head outside to show off your
new glow, be sure to apply some extra sunscreen. Another tip, a Sunless Tan will only last as long as the
“coloured” skin remains on the body so the use of moisturizers slowing
down the shedding process with prolong the tan.
What is sunburn?
Over the course of several hours, exposed skin turns bright red and
becomes extremely painful when touched. The skin will often feel very
warm as well. When you get sunburnt, you're basically killing skin cells. The
outer layer of skin on your body is called the epidermis. The outermost
cells of the epidermis -- the cells you see and feel on your arm, for
example -- are dead. But just below the dead cells is a layer of living
cells. These living cells continuously produce new dead cells to
replenish your skin. By sitting in the sun, you expose yourself to ultraviolet
light. Ultraviolet light has the ability to kill cells. Ultraviolet
light hits the layer of living cells in the epidermis and starts
damaging and killing them.
As your body senses the dead cells, two things happen:
1. Your immune system comes in to clean up the mess. It increases blood
flow in the affected areas, opening up capillary walls so that white
blood cells can come in and remove the damaged cells. The increased
blood flow makes your skin warm and red.
2. The nerve endings for pain begin sending signals to your brain. The
damaged cells release chemicals that activate pain receptors. This is
why sunburned skin is so sensitive.
The ways to avoid sunburn (without having to stay inside)
are to use a sunscreen, which blocks ultraviolet light, or pace
yourself so you get a tan first. When you get a tan, your body
essentially creates its own sunscreen using its own special pigment
cells in the epidermis.
How Sunburns and Sun Tans Work
With a nice tan you can go out in the sun and nothing happens unless
you have "fair skin". Unfortunately the fair skinned never get a tan,
so they always get sunburned unless they are wearing a sunscreen.
How Tanning Works (Caucasians)
When you get a tan, what is actually happening is that your melanocytes
are producing melanin pigment in reaction to ultraviolet light in
sunlight. Ultraviolet light stimulates melanin production. The pigment
has the effect of absorbing the UV radiation in sunlight, so it
protects the cells from UV damage. Melanin production takes a fair amount of time - that is why
most people cannot get a tan in one day. You have to expose yourself to
UV for a short period of time to activate the melanocytes. They produce
melanin over the course of hours. By repeating this process over 5 to 7
days pigment builds up in your cells to a level that is protective. In a variety of races melanin production is continuous, so
the skin is always pigmented to some degree. In these races the
incidence of skin cancer is much lower because cells are constantly
protected from UV radiation by melanin. Melanocytes actually produce two different pigments:
eumelanin (brown) and phaeomelanin (yellow and red). Red-heads happen
to produce more phaeomelanin and less eumelanin, which is why they
don't tan very well. In albinos, the chemical pathway that produces
melanin cannot proceed because an enzyme called Tyrosinase is missing. Melanocyte-stimulating hormone (MSH) is produced by the
pituitary gland. MSH flows through the bloodstream and reaches the
melanocytes, encouraging them to produce more melanin. The pituitary
gland is tied into the optic nerve, which means that it can sense light
resulting in the production of MSH. In fact a side effect of all of
this is that wearing sunglasses may make you more susceptible to
sunburn!
How Sunburn works
If you are Caucasian and you don't have a tan, then the cells in your
skin are not protected from the sun's ultraviolet radiation. You are
therefore an easy target for sunburn if you spend too much time in the
sun. As anyone who has sunburn knows, sunburn leaves your skin red and
extremely painful. In severe cases the skin forms blisters. When you get sunburn, your skin is actually damaged by UV
radiation and your body is responding to the damage. When you get
sunburnt, what you are really getting is cellular damage from
ultraviolet radiation. The body responds to the damage with increased
blood flow to the capillary bed of the dermis in order to bring in
cells to repair the damage. The extra blood in the capillaries causes
the redness - if you press on sunburned skin it will turn white and
then return to red as the capillaries refill. Evidence is now showing that the massive increase in skin
cancer is as a result of sun exposure some 20 – 30 years ago in the
majority of cases. This demonstrates the huge important of treating the
inviting sun with respect. Food for thought: Treat the sun with respect, always use
sunscreen, NEVER use the sun as a means to achieve a regular tan as
human nature suggest that most of us to expose the skin too much. For
cosmetic tanning, especially a tan that is required at short notice use
a sunless tanning product.
How Sunlight Works
Sunlight arrives on earth in three forms: infrared (heat), visible
light and ultraviolet. Ultraviolet light is classified into three
categories:
UVA (315 to 400 nm), also known as black light, which causes tanning
UVB (280 to 315 nm), which causes damage in the form of sunburn
UVC (100 to 280 nm), which is filtered out by the atmosphere and never reaches us.
99% of the sun's UV radiation at sea level is UVA. It is the UVB that
causes most of the problems related to sun exposure: things like aging,
wrinkles, cancer and so on, although research is increasingly
implicating UVA as well.
One of the interesting things about UV radiation is that it
is reflected by different surfaces. These reflections can amplify the
effects of UV exposure. For example, snow reflects 90% of UV light.
That is why you can get snow blindness and severe sunburns from skiing
on a sunny day. Sand can reflect up to 20% of UVB that hits it, meaning
that you can get extra UV exposure at the beach. On the other hand, certain things absorb almost all UV
radiation partially or completely. Glass is one of these substances,
which is why you cannot get sunburn in a greenhouse. Most sunscreens
use chemicals that have the same UV-absorbing properties.
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