Transcript Slide 1

Sunscreen
Sunscreens
• Sunscreens
Electromagnetic spectrum
Melanin
• Melanin
Melanin
• Melanin is a natural dark brown pigment
present in the skin.
• The photochemical reactions with which
we have the most direct sensory
experience are those that cause skin to
tan and burn due to more production of
the melanin.
• Excess exposure to Sun’s UV radiation
causes skin damage and skin cancer.
Melanin
• The infrared radiation from the sun that
strikes your body is felt as warmth.
• .
Vitamin D
• The ultraviolet radiation
causes photochemical
reactions to occur.
• 7-dehydrocholesterol
converted to vitamin D, the
"sunshine" vitamin
Vitamin D
Melanin
• The uv radiation activates specific
enzymes (certain proteins that
have specific biochemical tasks)
to photochemically convert
tyrosine, an amino acid
component of skin proteins, into
the compound melanin.
Melanin
• Melanin is brown in color and is
efficient at absorbing uv radiation
• the melanin sacrificially absorbs
the uv radiation, thereby protecting
the skin somewhat from further uv
damage
• such as burning or activation of
skin cancer formation.
Sunscreen Compounds
• Sunscreens sacrificially
absorb uv radiation,
• in the same way as melanin,
• protect the skin against uv
damage.
How does sunscreen work?
• By combining organic and
inorganic active ingredients.
• Inorganic ingredients like zinc
oxide or titanium oxide reflect or
scatter ultraviolet (UV) radiation.
• Among the inorganics, zinc oxide
offers much better UV-A protection
than TiO2.
Inorganic Sunscreen
• Newest TiO2 has a particle size distribution
between 40 and 50 nm, offering not only
good UV protection
• also avoids the occurrence of large particles
that give a whitening effect.
• The TiO2-coated mica pigment complements
and enhances light skin tones and gives a
more "natural" appearance to a beach
sunscreen,
Sunscreen
• Organic ingredients like
octyl methoxycinnamate
(OMC) or oxybenzone
absorb UV radiation,
dissipating it as heat.
Sunscreen
• Formulators often combine
inorganic and organic sunscreens
for a synergistic effect
• capable of achieving very high
SPF--sun protection factor-ratings.
Sunscreen
• Organic ingredients like
octyl methoxycinnamate
(OMC) or oxybenzone
absorb UV radiation,
dissipating it as heat.
• potential endocrine disrupters
Sunscreen
• Some sunscreens protect us from the two
types of damaging UV radiation: UV-A and
UV-B.
• Both UV-A and UV-B cause sunburns and
damaging effects such as skin cancer.
UV Radiations
• three types of wavelengths:
• UV-A: near UV region
wavelength
• Not absorbed by the ozone. It
penetrates the skin deeper than
UV-B. 320-400 nm
• Tanning
UV-B
• Responsible for sunburns.
• It is partially blocked by the
ozone layer.
• 280-320nm
UV-C
• Far UV .
• totally absorbed by the
earth's atmosphere;
• we encounter it only from
artificial radiation sources.
200 – 280 nm
Factors affecting UV Radiations
•
•
•
•
•
•
Stratospheric Ozone
Time of the day
Time of the year
Latitude
Altitude
Weather conditions
UV INDEX
Purchasing Sunscreen
• the Sun Protection Factor
or SPF measures how
effectively the sunscreen
formula limits skin
exposure to UV-B rays
that burn the skin.
•
Sunscreen
• The higher the SPF the
more protection the
sunscreen will provide
against UV-B rays.
• SPF does not measure
UV-A.
Sunscreen
• If you are looking for UV-A
protection,
• purchase a product that
has broad-spectrum
protection.
Sunscreen Compounds
• Uv light also produces photochemical
reactions within the eye that produce
cataracts and retinal damage.
• Dark sunglasses do not necessarily
filter out uv radiation.
• Those that are made specifically to
filter out the damaging uv radiation
should always be used.
PABA
• The first sunscreen developed, paraaminobenzoic acid (PABA),
• fell out of use because it stained clothing
and was found to cause allergic reactions
in some people.
avobenzone
known as Parsol 1789, as a UVA absorber.
Butyl methoxy dibenzoylmethane
PABA
• the para-aminobenzoic acid esters
(primarily octyl dimethyl paraaminobenzoic acid) are commonly used in
many formulations
• and have not been associated with the
solubility and sensitivity problems of PABA
PABA
• Para-Aminobenzoic Acid
• serve as a nutrient for the
intestinal tract's numerous
microorganisms.
•
PABA
• increases the intestinal
synthesis of other B vitamins,
particularly of folic acid, of
which it is a structural unit.
Folic acid showing PABA
PABA ester
can eliminate the irritation and staining problems.
PABA
• Contains conjugated carbon: single and
double bonds
• The wavelength of radiation absorbed
depends on the number of conjugated
double bonds
• Wavelength max for PABA ~ 265 nm
• Wavelength max for Vit A ~ 500 nm 11
double bonds
PABA
•
•
•
•
•
•
PABA absorbs strongly ~240-290 nm
Maximum absorption ~ 265nm
Protects in Far UV 200-280 nm
Does not protect ~310 nm
burning of skin
Need more effective mixture of
compounds
Retinal 11 conjugated double
bonds; max 500 nm
Greater the number of double
bonds; longer the wavelength
absorbed
Sunscreen Compounds
• 2-ethylhexyl-p-methoxycinnamate
• 2. oxybenzone
Sunscreen
• 4-MBC potential endocrine disrupters
Suncreen
• Sitting behind the window
• Reddening of the skin /not a
sun burn
• Glass does not transmit much
light of wavelength below 350
nm
When To Apply Sunscreen
• Apply sunscreen approximately 30 minutes
before being in the sun (for best results) so
that it can be absorbed by the skin and less
likely to wash off when you perspire.
• Remember to reapply sunscreen after
swimming or strenuous exercise.
• Apply sunscreen often throughout the day if
you work outdoors, and wear hats and
protective clothing.
How To Apply Sunscreen
• Shake well before use to mix particles that might be
clumped up in the container. Consider using the new
spray-on or stick types of sunscreen.
• Be sure to apply enough sunscreen. As a rule of
thumb, use an ounce (a handful) to cover your entire
body.
• Use on all parts of your skin exposed to the sun,
including the ears, back, shoulders, and the back of
the knees and legs.
• Apply thickly and thoroughly.
• Be careful when applying sunscreen around the
eyes.
What is an SPF?
• SPF stands for Sun Protection Factor.
Sunscreens are rated or classified by the
strength of their SPF. The SPF numbers
on the packaging can range from as low
as 2 to greater than 50. These numbers
refer to the product’s ability to deflect the
sun’s burning rays.
SPF
• The sunscreen SPF rating is
calculated by comparing the
amount of time needed to
produce a sunburn on
sunscreen protected skin
• to the amount of time needed
to cause a sunburn on
unprotected skin.
SPF
• if a sunscreen is rated SPF 2 and a
fair-skinned person who would
normally turn red after ten minutes
of exposure in the sun uses it,
• it would take twenty minutes of
exposure for the skin to turn red.
• A sunscreen with an SPF of 15
would allow that person to
multiply that initial burning
time by 15, which means it
would take 15 times longer to
burn, or 150 minutes.
SPF
• PF Math
• SPF Number x Time to Burn Without Sun
Protection = Time to Burn while wearing
sunscreen*
• *assuming that sunscreen is applied
properly
SPF
• Percentage of Protection from
damaging UV rays:
SPF 15 = 92%
SPF 30 = 97%
SPF 40 = 97.5%