SUNSCREENS:
CLASSIFICATION & SUN PROTECTION
M pharm I year
Dept. Of pharmaceutics
Associate Professor
Dept. of Pharmaceutics
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INTRODUCTION
•Visible sunlight is only a tiny part of the whole radiation spectrum
emitted by the sun(400–700nm). By increasing wavelength greater than
700nm, one enters the invisible radiation range called infrared
radiation(IRR); by decreasing wavelength lesser than 400nm, one enters
the ultraviolet radiation(UVR) domain.
•Sun rays have both beneficial & harmful effects on human body depend
on length & frequency of exposure, intensity of light & sensitivity of
individual.
•These rays stimulate blood circulation in derma, cause development of
Vitamin A from provitamins, increases formation of Hb.
•Moderate exposure of sunrays cause thickening of skin by producing
melanin which ultimately increases body’s natural protective mechanism
against sunburns.
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•Overexposure to the sun’s invisible rays can
be harmful to human skin. The damage can be
immediate with visible effects, such as
erythema and sunburn, leading to cell and
tissue degradation. The damage can also be
long term, and the cumulative effects of
prolonged exposure are now increasingly
recognized to be the possible cause of
degenerative changes in the skin such as
premature wrinkling and skin cancer. Indeed,
many skin changes that often are identified
with aging actually result from damage by too
much sun exposure.
•Natural protection from sunburn by body is
through increasing thickness of stratum
corneum & pigmentation of skin.
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UV RADIATIONS
•UVR from both sunlight and artificial sources is
subdivided into three sections termed “UVA,”
“UVB,” and “UVC” from the longer to shorter
wavelengths:
UVA from 400 to 320 nm,
UVB from 320 to 290 nm, and
UVC less than 290 nm.
The UVA section is further divided in two
subsections: UVA I (longer wavelengths 400–340
nm) and UVA II (shorter wavelengths 340–320 nm).
The longer the wavelength and the higher the
number, the deeper the UV penetrates the skin. The
shorter the wavelength and the lower the number,
the greater the energy level of the light and the
more damage it can do. the amount of UVA
reaching the earth’s surface may be considered to
be 10 to 30 times greater than that owwfw U.DuVloMBix ..c om 4
UVA / LONGWAVE (320-400 nm)
• Weak Erythrogenic Activity / Low Energy Waves
• Primary TANNING component ; Tan is injury by ROS to the Skin DNA; imperfect
attempt to prevent further DNA damage.
• Penetrates deeper than UVB ; DERMIS
• Tanning, photo aging
• Effects of UVA manifest usually after a long duration of exposure, even if doses are
low.
• Studies have shown that UVA impairs the antigen presenting cell (APC) activity of the
epidermal cells and thereby causes immune suppression, thus contributing to the
growth of skin cancer.
• UVA induces significant photo biological reactions, mostly of indirect nature and
requiring the presence of oxygen, such as immediate and delayed tanning reactions
and new melanin formation.
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UVB / MEDIUMWAVE (290 -320 nm)
• Erythrogenic activity is the highest; Most severe damage
• Primary BURNING component
• Sunburn, Vit D synthesis
• Responsible for inducing skin cancer
• Direct impact on cell DNA and proteins
• UVB is the principal cause of acute sunburn and tanning . Therefore, sunscreen
efficacy is predominantly directed against UVB radiations (the relative contribution
of UVA radiation to sunburn is considered to be only 15–24%).
• In addition, exposure to UVB radiation is immunosuppressive, mutagenic, and
carcinogenic.
UVC / SHORTWAVE (100-290 nm)
• Absorbed near-totally by Stratospheric Ozone
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WHAT ARE SUNSCREENS ?
• SUNSCREEN, also known as sunblock, sun cream or suntan lotion, is
a lotion, spray, gel, foam, or other topical product that absorbs or
reflects some of the sun’s ultraviolet (UV) radiation & thus helps
against sunburn.
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PRINCIPLE OF EFFECTIVENESS OF SUNSCREEN
•Protective layer can be provided to skin that prevent UV rays to reach the
skin. Ex: zinc oxide
•Incorporation of substance that filter sun rays by absorbing UV range 280-
320nm but allow higher range to pass
•Substance to prevent symptoms of inflammation without reduction of
tanning as damage of cell liberates histamine in tissue which can be
treated by antihistamines.
•Substance such as 8-methoxypsoralene can be taken before exposure to
sun , which accelerates tanning but avoid sunburn.
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SUNBURN PREPARATIONS
Sunburn & suntan preparation classified as:
1.palliatives preparations
2.stimulative preparations
3. sunscreen preparations
Palliative preparations: used for relief of irritation & other problem caused
from sunburn.
Stimulative preparations: they are artificial suntan preparations , which is
of great demand in western countries.
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SUNSCREEN PREPARATION AND APPROVED
AGENTS
•sunscreen preparation are most important of all preparations. It should
scatter incident light effectively or should absorb erythemal portion of
sun’s radiant energy.
•Opaque powders such as zinc oxide is most effective as it will scatter or
reflect the UV light falling upon it. (also known as physical mechanism)
•PABA & its ester which will absorb UV radiation. (also know as chemical
mechanism)
•Ideally, sunscreen agent :
-should be non toxic & stable.
-absorb range over 280-320 nm
-should be neutral & readily soluble in suitable vehicle.
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IDEAL SUNSCREEEN
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SUNSCREEN PREPARATION
•Solution type: it can be prepared simply by mixing & dissolving
sunscreen agents , other ingredients in suitable vehicle.
•Cream type: it is an emulsion type by taking oily phase & aqueous phase
separately & heated to liquify and then mixed with stirring.
•Gel type: it is highly viscous aq.preparation, in which thickening agent is
seperately dispersed in water & then mixed with other ingredients.
•Lotion type: it can be solution or emulsion type of preparations where
solution is prepared by simply mixing & emulsion by seperately heating aq
& oily phase at same temperature and slowly mixed with stirring.
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SUNSCREEN LOTION
•Sunscreen lotion is a topical product that absorbs or reflects some of the sun’s
ultraviolet(UV) radiation and thus helps protect against sunburn. Diligent use of
sunscreen can also slow or temporarily prevent the development of wrinkles, moles
and sagging skin.
•The sun protection factor (SPF rating, introduced in 1974) is a measure of the fraction
of sunburn-producing UV rays that reach the skin. For example, “SPF 15” means that
1⁄15of the burning radiation will reach the skin, assuming sunscreen is applied evenly
at a thick dosage of 2 milligrams per square centimeter(mg/cm2).
•The SPF can be measured by applying sunscreen to the skin of a volunteer and
measuring how long it takes before sunburn occurs when exposed to an artificial
sunlight source.
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ORGANIC SUNSCREENS
UVB FILTERS
PABA derivatives – Padimate-O most potent UVB absorber
Cinnamates – Octinoxate (Most frequently used sunscreen ingredient) Cinoxate
Salicylates – Octisalate, Homosalate, Trolamine salicylate
Octocrylene
Ensulizole
ORGANIC SUNSCREENS
UVA FILTER
Benzophenones (UVB and UVA2 absorbers)
Oxybenzone (Absorbs UVB and UVA II both)
Sulisobenzone, Dioxybenzone
Avobenzone or Parsol 1789 (UVA1 absorber)
Meradimate or Methylanthranilate (UVA2absorber)
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INORGANIC (PHYSICAL) SUNSCREENS
Zinc oxide
Titanium dioxide
Others – iron oxide, Petrolatum, kaolin, calamine, Ichthammol (Aluminium
Bituminosulfate), talc.
Inorganic agents function by reflecting, scattering or UV
radiation (Opaque)
Their opaque nature and “whitening effect” are an inherent
disadvantage, which may be minimized by the use of
micronized or ultrafine particles.
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SUN PROTECTION FACTOR (SPF)
•SPF measures sunscreen protection from UVB rays, the kind that cause sunburn and
contribute to skin cancer. SPF does not measure how well a sunscreen will protect from
UVA rays, which are also damaging and dangerous. Dermatologists recommend using a
SPF15 or SPF30 sunscreen. Higher SPFs don’t provide much more protection.
MED of Photoprotected Skin
Sun Protection Factor (SPF) =
MED of Unprotected Skin
MED is minimum dose of radiation which produces erythema
SPFs are determined indoors using xenon lamps which approximate the spectral quality
of UV radiation
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•Sunscreens with really high SPFs, such as SPF
75 or SPF 100, do not offer significantly greater
protection than SPF 30 and mislead people into
thinking they have more protection than they
actually do.
Additionally, in order to have broad spectrum
protection, the UVA protection should be at
least 1/3 of the UVB protection.
High SPF sunscreens usually offer far greater
UVB than UVA protection, thus offering a false
sense of full protection.
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Factors which influence effectiveness of SPFs
•Difference in skin types.
•Thickness of the applied sunscreen.
•Time of day.
•Altitude: each 1,000 ft increase adds 4% to the intensity of erythema
producing UV radiation; thus intensity is about 20% greater in Pocatello
than at sea level.
•Environment: snow/white surfaces reflect 70-90%, and when directly
overhead water reflects nearly 100% of UVR.
•Vehicle: determines skin penetration of sunscreen.
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REFERENCES:
❑B.M. Mithal, ”A Handbook of Cosmetics” ,90-105
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THANK YOU
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