28 - 197 - PHOTOPROTECTION Flashcards
peak UV hours
10:00 AM to 2:00 PM
wavelength of UVB
290 - 320 nm
wavelength of UVA2
320 - 340 nm
wavelength of UVA1
340 - 400 nm
accounts for 5% to approximately 10% of the UV light that reaches the surface of the earth
UVB
accounts for **95% of the UV that reaches the surface of the earth **because it can penetrate through clouds and glass windows, and is not obstructed by the ozone layer
UVA1
this UV is present all the time, regardless of cloud cover or other obstruction
UVA1
it is more likely to cause pigmentation than any other wavelength
UVA1
it induces reactive oxygen species (ROS), which cause damage to blood vessels, collagen fibers, and elastic fibers located deep under the skin, and are involved in skin aging
UVA1
An ideal photoprotection method
avoid sunlight
UV decreases by _% as the latitude increases by _°
UV decreases by** 3%** as the latitude increases by 1°
ecause atmosphere becomes thinner as altitude increases, UV increases by 4% every 300 meters from the horizon.
Snow, sand, and metal can reflect up to 90% of UV.
UV is reduced by 50% to approximately 95% under the shade; hence, one should stay in the shade if possible
formula for SPF
SPF is the ratio of the minimal erythema dose (MED) of a subject’s sunscreen-protected skin over the MED of the unprotected skin.
Current FDA guidelines specifically require that products be tested using a solar simulator with emission spectrum covering the wavelength range of 290 nm to 400 nm, and that the sunscreen product be applied at a concentration of 2 mg/cm2 .
what is the concentration of sunscreen specified for SPF testing
**2 mg/cm2 **- equivalent of 1 oz (30 mL) of sunscreen to cover the entire body surface
SPF15 blocks how many percent of UVB
93.3%
SPF30 blocks how many percent of UVB
96.7%
SPF is accepted as the worldwide standard for the assessment of protection against the erythemogenic effects of what UV rays?
UVB and UVA2
what method is used to evaluate protection against UVA?
persistent pigment darkening (PPD) method
UVA protection factor formula
In the PPD method, the dose of UVA required to induce PPD observed 2 to 24 hours after exposure of s**unscreen-protected skin is compared to that of sunscreen-unprotected skin; **the ratio is then expressed as the UVA protection factor
The European Union requires UVA protection factor to be at least ____ of the labeled SPF, with the PPD method as the assessment of the UVA protection.
one-third
To label a sunscreen product as “broad spectrum,” it should have a critical wavelength of at least ____ nm.
370 nm
wavelength at which the area-under-the-absorbance-curve represents 90% of the total area-under-the-curve in the UV region
critical wavelength
the nomenclature used in the FDA Sunscreen Monograph
United States Adopted Name (USAN)
2 catrgories of UV filters
- Organic (chemical) Filters
- Inorganic (physical) Filters
The most widely used UVB filter worldwide
octinoxate (ethylhexyl methoxycinnamate)
the most widely used UVA filter
oxybenzone (benzophenone-3)
Weak UVB absorbers; good substantivity—used in water-resistant sunscreens and hair-care products
Trolamine salicylate
Water soluble; enhances sun protection factor of the final product
Ensulizole
Most commonly used UVA filter
Oxybenzone
most common cause of photoallergic contact dermatitis to UV filters
Oxybenzone
Photounstable; enhances the photodegradation of octinoxate
Avobenzone
what are examples of inorganic filters?
- Titanium dioxide
- Zinc oxide
has lower refractive index compared to microfine titanium dioxide and thus appears less white
micronized zinc oxide
When the size of inorganic filter is larger than ____ nm, they can protect skin from all the wavelengths of UV
200 nm
Give one advantage of inorganic filters
Inorganic filters are not allergenic and do not react with skin, and are thus recommended for children and adults with allergies.
However, inorganic filters are not preferred and are restricted in use because they leave a white coating behind.
If applied too often, they may be comedogenic.
Give examples of UV filters that are unstable and degrades during UV exposure
-
avobenzone (butyl methoxydibenzoylmethane; Parsol 1789)
*** padimate O **(ethylhexyl dimethyl PABA) - octinoxate (ethylhexyl methoxycinnamate)
It is possible to incorporate other agents to increase the photostability of the final product (Fig. 197-3).
Most of these agents are photostable UV filters (eg, octocrylene, salicylates, oxybenzone) that absorb photons to minimize the effect on the photounstable UV filter; they also serve as receptor molecules for energy transfer from excited state photounstable filter, hence minimizing the photodegradation of the latter
most common causes of UV filter photoallergy
Octocrylene, oxybenzone (benzophenonone-3), and avobenzone (butyl methoxydibenzoylmethane)
No photoallergy has been reported with inorganic UV filters (titanium dioxide and zinc oxide).
what will you advice regarding the use of sunscreens in children younger than age 6 months
For this group of patients, it is prudent to use other means of photoprotection, such as clothing
what is the sunscreen option for children less than 2 years old
Children younger than 2 years old should use inorganic sunscreen rather than organic sunscreen.
The peak action spectrum for previtamin D synthesis
300 ± 5 nm
MED and frequency of sun exposure sufficient for humans to produce the daily needed Vitamin D
The amount of UVB required to produce daily needed vitamin D in humans is not so much; exposure of 0.33 or 0.5 MED 2 or 3 times a week to arms, hands, and face is sufficient.
In other words, a person with skin type II who lives in Boston needs only 5 minutes at noon in July.
According to another study, arms and legs can create 3000 IU by being exposed to 0.5 MED of UVB.
Therefore, lightskinned people can produce sufficient vitamin D by staying under midday sunlight for 5 to approximately 30 minutes, twice a week.
For those individuals who are concerned or are at risk for vitamin D insufficiency, a balanced diet and a daily ____ IU vitamin D 3 supplement, along with __ g of calcium, is recommended
** 600 IU **vitamin D3 supplement, along with **1 g **of calcium
Active Ingredients for Oral Photoprotection
examples of flavonoids
■ Catechins
■ Isoflavones (genistein, silymarin)
■ Proanthocyanidins
examples of Nonflavonoids
■ Phenolic acid (benzoic, gallic, and cinnamic [caffeic, ferulic, and p-coumaric] acids)
■ Resveratrol
this flavonoid is mainly present in tea leaves
Catechins
The major active component of silymarin
silibinin, which has been shown to protect against photocarcinogenesis in animals
this is a group of substances widely present in grape seeds
Proanthocyanidins
This nonflavonoid appear mostly in red wine and tea
Phenoic Acid
stilbene found in grapes, red wine, and nuts, is also a potential polyphenolic antioxidant
Resveratrol
examples of nonpolyphenolic phytochemicals
carotenoids and caffeine
the in-vitro measurement used in many countries to quantify the ability of fabrics to protect against UV
UV protection factor (UPF)
What UPF is classified as having “good protection”?
UPF15 to UPF24
What UPF is classified as having “very good protection”?
UPF25 to UPF39
best UV absorber garment
Polyester fibers
poorest UV absorber garment
cotton and rayon
What UPF is classified as having “excellent protection”?
UPF40 to UPF50+
Laundering garments made from** cotton or rayon** _ _ _ _ _ the UPF because of shrinkage, causing a decrease in the porosity of the fabrics
increases
Wetness _ _ _ _ _ the UV protection of a light-colored (especially white) garment
decreases
This is because the protective effect of white cotton fabric is mainly from light-scattering at the fiber–air interface: when wet, the fabric no longer scatters light and the garment becomes more transparent to both UV and visible light
In contrast, dark-colored garments absorb light and thus do not become see-through or provide less UV protection when wet.
what UV ray is absorbed by the cornea?
UVB
Mainly UVB is absorbed by the cornea to damage it; in addition, UVA, the longer UV wavelengths, damages the lens and further provokes cataracts.
what UV ray damages the lens?
UVA
Mainly UVB is absorbed by the cornea to damage it; in addition, UVA, the longer UV wavelengths, damages the lens and further provokes cataracts.
What rays impair the retina?
Visible and infrared rays
to protect the retina, what color of sunglasses should be worn?
Consequently to protect the retina, yellow-colored or red-colored sunglasses, which can block blue or purple light, are preferred.
time of maximum UV exposure to the eye
8:00 and 10:00 AM and 2:00 and 4:00 PM, when solar radiation is parallel to the eye
The amount of visible light transmitted through the lens
luminous transmittance
a lens with 20% luminous transmittance would allow 20% of the visible light to pass through
The standard requires that the UVB transmittance be __% of the luminous transmittance
5%
Lenses are grouped into 5 categories (0 to 4), ranging from fashion sunglasses (lens category 0) to specialpurpose sunglasses for very high sun-glare reduction (lens category 4); category 4 lenses are not to be worn during driving.
Category 0 lenses are allowed to have luminous transmission of 80% to 100%, whereas category 4 transmission is limited to 3% to 8%.
The standard also mandates that the minimum vertical diameter for adult sunglasses is ___ mm, and for children, ___ mm.
adult - 28 mm
children - 24 mm
Dietary supplementation with at least ____IU/day of vitamin D 3 (cholecalciferol) is thus recommended for all patients with photosensitive disorders who avoid sun and use sunscreens
at least 400 IU/day of vitamin D 3
provided safe and effective photoprotection through eumelanin synthesis in patients with erythropoietic protoporphyria
Afamelanotide (analog of human α-melanocyte–stimulating hormone)
