Use of Sunscreen in dermatology

1. Sunscreens
DR. SHRADDHA KALE

2. Electromagnetic spectrum or solar
spectrum of the Sun
400nm-
700 nm
700-2500nm

4. Near UVA Far UVA
290nm
(<9% of total solar
irradiance)
(100-400nm)

5. Depth of Penetration of
UV Light
• depends on its
wavelength (i.e., longer
the wavelength, deeper
the penetration)
•UVA, VL, and IR (longer
wavelengths) penetrate
deeper (up to the
subcutaneous tissue) than
UVB (shorter )

6. Photobiological Reactions
• Biological effects of UVR are more pronounced
with the light of shorter wavelength as it
contains a high quantum of energy.
• To produce the same degree of erythema, the
dose of UVA required is 1000 times higher
than that of UVB while VL fails to produce
erythema even at that dose.

8. DEFINITION
• Sunscreens are agents that alter the effects of
UV radiation on the skin by absorption or
reflection of part of the incident radiation

9. Sunscreen Indications
Protection from ultraviolet radiation to prevent the
following:
• Sunburn- FDA Approved
• Skin or lip damage, freckling, skin discoloration—
FDA-approved
• Skin aging—FDA-approved
• Skin cancer—FDA-approved
• Phototoxic or photoallergic drug reactions
• Photosensitivity diseases
• Photoaggravated dermatoses

10. Contraindications
• Known sensitivity to any active sunscreen ingredient or
vehicle
• Infants < 6 months of age (sun avoidance is most
appropriate for very young infants)
• As the sole component of an overall program of
photoprotection
• Individuals wearing sunscreen may stay in the sun much
longer and ‘outlast’ the protection of their sunscreen with
resultant skin cancer risk. Hence, always recommend a
comprehensive sun protective strategy that includes sun
avoidance, seeking shade, wearing protective clothing,
along with using sunscreens

11. An ideal sunscreen
• Broad-spectrum coverage
• Combination of physical & chemical sunscreens
• Photostability
• High substantivity
• Cosmetically elegant
• Non-irritant
• Hypoallergenic
• Noncomedogenic
• Economical

12. Measuring Sunscreen Efficacy
• UVB protection offered by sunscreens is
measured by the SPF and substantivity
• UVA Protection Indices-
• In vivo testing methods: IPD, PPD, and PFA
• In vitro method- Diffey critical wavelength
determination.

13. SPF – SUN PROTECTION FACTOR
• SPF is a numerical rating system to indicate the degree of
protection provided by a sun care product.
• It is defined as the ratio of the least amount of UV energy
(UVB) required to produce minimal Erythema on
sunscreen-protected skin to the amount of energy required
to produce the same erythema on unprotected skin.
• As UVB is approximately 1000 times more erythemogenic
as compared with UVA, the SPF is largely a measure of
protection against UVB.
• SPF= MED of photoprotected skin/MED of unprotected skin

14. • Important factor in
photoprotection is not how
much is blocked by sunscreen,
but how much is prevented
from being absorbed into skin.
• For SPF15, 6.7% is absorbed
into skin, whereas for SPF30,
3.3% is absorbed, which is only
half the amount.
• Also, the amount of UVB
needed to cause DNA damage
that results in skin cancer is less
than the amount needed to
cause erythema.
• Moreover, the amount of
sunscreen people use is always
less than 2 mg/cm2. Therefore,
it is more helpful to choose
sunscreen with the highest SPF
available.
Ultraviolet B absorption (as a %) =
100—(100/SPF).
SPF UVB Absorption
%
2 50
4 75
8 87.5
15 93.3
20 95
30 96.7
50 98

15. Adherent property or substantivity
• Ability of a sunscreen to maintain efficacy and withstand
adverse conditions such as exposure to water and sweat.
• The FDA classifies the terms “water-resistant” and “very
water-resistant” depending on the substantivity.
1. Water-resistant sunscreens: ability of a sunscreen to retain
its photoprotective properties following
two 20 minutes intervals (40 minutes total) of moderate
activity in water immersion.
2. Water proof sunscreens or very water-resistant:
doubling aquatic activity time to four 20 minutes activity
intervals (80 min total).
• The FDA permits products labeled as waterresistant or very
water-resistant to be grouped together under the same term
“sweat resistant”

16. Factors affecting substantivity
1.Base and additives: Sunscreen preparations with a
polyacrylamide base are highly substantive to the skin and
tend to resist washing off after sweating and swimming.
2. Emollients: decreases substantivity.
3. Formulation: The formulation influences not only the
substantivity but also the SPF and cosmetic acceptability of
the sunscreen.
• Lotions are non-greasy, spread easily, and are cosmetically
more acceptable but their SPF is generally 15 or less,
whereas sunscreens with higher SPF are greasier and less
acceptable.
•Oil-free gels are preferable in acne prone and oily skinned
individuals but the SPF of such preparations is lower.

17. a. Japanese standard (PPD; in vivo
method):
UVA dose that induces pigment darkening 2–24
hours after exposure in sunscreen-protected
skin
UVA dose that induces persistent pigment
darkening 2–24 hours after exposure in
unprotected skin

18. • A ‘broad-spectrum’ sunscreen is defined as
any product that demonstrates an in vitro
critical wavelength of 370 nm or greater.
• The critical wavelength is defined as the
wavelength at which 90% of the total area
under the absorbance curve resides, with the
absorption measures across the UV spectrum
ranging from 290 to 400 nm.
Diffey critical wavelength

20. • IPD(Immediate Pigment Darkening) describes the immediate gray-
brown pigmentation of the skin as caused by the oxidation of
preformed melanosomes in the skin.
• Caused primarily by UVA and short wavelength of VR
• Begins soon after UVR exposure and lasts upto 2 hours
• The transient nature of IPD which requires immediate testing makes
it a less than ideal measurement tool of UVA protection.
• • Persistent pigment darkening (PPD) occurs if pigmentation persists
more than 2 hours (higher UVA fluencies 8–25 J/cm2).
• PPD is measured between 2 and 24 hours following irradiation and
has the added benefit of simultaneously evaluating sunscreen
photostability. However, PPD requires subjects be exposed to high-
intensity lamps for long periods of time (up to 1 hour).
• The PFA has a less inclusive endpoint following UVA irradiation,
measuring either erythema or pigmentation (tanning). Like PPD, it is
evaluated 24 hours after light exposure.

21. The United Kingdom uses a variation
of this in vitro test called the Boots star
rating.
The Star system is a ratio of two in
vitro tests:
The ratio of a product’s UVA
absorbance to its UVB absorbance.
Products with better UVA absorbance
have a higher Boots star rating

22. b. Australian/New Zealand standard (in vitro
method):
• A 8 mm layer of the product should not transmit
more than 10% of radiation of 320–360 nm or 20
mm layer of the product should not transmit
more than 1% of radiation of 320–360 nm.
c. European Union guidelines:
UVA protection factor (PPD method) = 1/3 of SPF
and critical wavelength = 370 nm.

23. LABELING

24. PA –protection factor for UVA classified as PA+, PA++,
or PA+++
VERY

25. Classification
Mode of action
Organic (chemical)
(absorption of UVB,
UVA2)
UVB sunscreens
(absorb the entire UVB
spectrum)
Homosalate
Octocrylene
Ensulizole
Octisalate
Octinoxate
UVA sunscreens
(absorb short
UVA)
Oxybenzone
Mexoryl SX
Avobenzone
Meradimate
Inorganic (physical)
(reflect/scatter UVB,
UVA1&2)
Titanium
dioxide
Zinc
oxide
combinat
ion
sunscree
n

28. CHEMICAL
SUNSCREEN
•DEF- These contain one or more chemicals, which
absorb specific wavelengths (absorption spectrum) of
UVR and convert into heat, not allowing them to reach
the viable cells of the epidermis.
•CLASSIFICATION- UVB sunscreens(absorb entire UVB
spectrum) and UVA sunscreens (limited absorption
spectrum, primarily absorbing shorter wavelengths
of UVA (320–360 nm).
Hence, it is easier to protect
against UVB and short UVA than against longer
UVA (360–400 nm).
DISADVANTAGE- Less useful in photodermatosis due to
poor UVA action

29. 2nd most potent UVB absorber
Weak, high conc. req
Thick, oily
Because others are lipid soluble and greasy, this
is water soluble and less oily
M.potent
UVA2
UVA1 Lower RI, appear
less white
ECAMSULE

30. •Avobenzone is photounstable, it
cause degradation of other sunscreen
ingredients like octinoxate.
•Octocrylene plays role in stabilizing
avobenzone.
•Without octocrylene, avobenzone is
degraded by 50% upon 1 hour of UV
exposure, rendering the sunscreen
less effective.

31. Inorganic (Physical) Sunscreens
• Aka sun blocks
• formulations containing opaque particulate ingredients
such as zinc oxide, titanium dioxide (5–20%), talc,
magnesium oxide, kaolin, and ferric chloride.
• zinc oxide and titanium dioxide are most frequently used.
• act primarily by reflecting and scattering UV and VR,
though some chemicals also exhibit absorptive properties.
• Barium sulfate and talc attenuate VR and UVR only by
scattering.
• Titaniumdioxide and zinc oxide exhibit a semiconductor
optical absorption gap, absorbing most radiation between
290 and 400 nm but scattering most of the radiation of
longer wavelengths (VR).

32. Factors affecting effectiveness of
inorganic sunscreens
1. Reflective index: Sunscreens with a higher reflective index
have better protection but are cosmetically less accepted.
Ex-Titanium dioxide has a higher reflective index than zinc
oxide and is less cosmetically acceptable.
2. Particle size: Micronized pigment-containing sunscreens
offer good protection against UVB induced immuno-
modulation.
Ex-Microfine zinc oxide protects over a wide range of UVA
including UVA1, while microfine titanium dioxide protects
against UVA2.
3. Dispersion in base.
4. Film thickness.

33. Advantages
• chemically inert, safe, and absorb or reflect
through the full UV spectrum
• are suitable for patients with sensitive skin and in
very young children
• Vitiligo on the Sun-exposed parts- use physical
sunscreens after psoralen phototherapy.
• Also protect against VL-aggravated dermatoses
such as porphyrias
• They are not easily washed off when the skin is
immersed in water but give limited protection if
the sun exposure is extended beyond 2 hours.

34. Disadvantages
• Poor cosmetic acceptance (gritty consistency & leave a
mask-like residue on the skin)
• Overcomed by-
1.Adding other pigments, such as iron oxide, that simulate
flesh tones may partially camouflage this effect
2.Reducing the particle size of chemical to a microsize or
ultrafine grade and making it less visible on the skin
surface, microsized (‘nanosized’).
3.But Changing the form results in their functioning by
absorption and not simply blocking UVR, making TiO2
less effective in the UVA range than an opaque physical
blocker. Even with this limitation, this ingredient can be
classified as a broad-spectrum agent.
4.Using combination sunscreen

36. Sunscreen Vehicles
• Determine sunscreen efficacy – affect uv
absorption of active agents
• Esthetics
• Durability
• Water resistance

37. Emulsions.
• The most commonly used sunscreens are lotions (thinner,
less greasy, large body area) and creams.
• Oil-in-water and water-in-oil emulsion
• Since sunscreen ingredients are oil soluble, most products
are oil in water emulsions
• Higher-SPF=more sunscreen oils=more stickiness( heavy,
greasy feel )
• So-called dry lotions, often labeled ‘sport lotions,’ are an
attempt to formulate a less oily product using newer
polymeric film formers and less greasy silicone oils.
• Newer ‘ultrasheer’ products further refine these qualities
with the use of silica as a major vehicular component.

38. Gels
Disadv-
• Easily removed by swimming or perspiration
• Tend to more readily cause facial or eye stinging.
Adv-
• Favored by individuals with oily skin or those who
are acne prone.
• Easier to use for individuals with thinning scalp
hair or abundant body hair.

39. Nanoparticles in Sunscreen
Advantage-
• No white cast
• Vehicle is more transparent, less viscous, and
blends into the skin more easily.
Disadvantage-
• Because of their diminutive size, Nanoparticles
may evade the human body’s natural clearance
modalities and immune defenses, so it possesses
greater harm.

40. Sprays
Adv-
• convenience of application
• useful for forehead application to minimize stinging of the
eyes, and for scalp areas with thinning hair
Disadv-
• difficult to apply evenly
• can produce a discontinuous film, resulting in a less
effective sunscreen product.
The FDA has not approved sprays as a dosage form

41. Sticks
Thickened with waxes and petrolatum
most lipid-soluble sunscreens can be readily incorporated into
sticks.
Sticks are helpful for protecting limited areas of the body, such as
the lips, nose, or around the eyes.
Cosmetics.
Adv- Daily protection , superior esthetics, better compliance with
their use, commercially available to consumers yearround,
Foundation make-up, without UV filters and SPF designation,
may provide some protection (generally around SPF,4–5)
because of its pigment content.
By raising the level of pigments (including TiO2), or by adding a
chemical sunscreen, a higher SPF can easily be achieved.
By virtue of its opacity, foundation make-up also provides the
benefit of some UVA protection.

42. Adverse Reactions To Sunscreens
• Subjective irritation(m/c)—immediate stinging, burning,
itching on application, without associated visible erythema.
(eye area m/c)
• Contact urticaria (Erythema occurring imm. on contact)—
immunologic (IgE mediated)/ nonimmunologic (toxic or direct
mast cell degeneration)
• ICD/ACD
• Photosensitivity (oxybenzone- m/c/c, Octocrylene &
Avobenzone )
• Acnegenicity (induce or exacerbate acne)/Comedogenicity
• Contact folliculitis- rapid onset of small follicular papules and
pustules shortly after product application- reduced by gels
and spray
• Low levels of Vit D

43. • Sunlight, specifically UVB at
310 nm, is a major source of
the biosynthesis of active
vitamin D3.
• Sunscreen effectively blocks
UVB absorption and thereby
reduces or shuts down vitamin
D synthesis in the skin.
• Patients may get UVR through
noncovered areas to maintain
adequate vitamin D levels.
• For individuals practicing
rigorous photoprotection,
daily intake of vitamin D
through diet or supplements
of 600 IU needed.
• For those 71 years of age and
older, 800 IU is recommended.

44. Instructions To Patients Regarding Sun
Protection Measures
• Sunscreens are most important from 10:00 AM to 4:00 PM (day light savings time) when the sun’s rays
are strongest. avoid significant sun exposure during these peak hours, by staying in the shade or
indoors.
• For intermittent, casual daily use, a sun protection factor (SPF) 15 sunscreen is sufficient.
For prolonged recreational exposures, an SPF 30 is more desirable, particularly for fair-skinned
individuals.
• Sunscreen should be applied 15 to 30 minutes before sun exposure to allow sufficient time for the
protection to develop, and subsequently reapplied every 2 hours.
• Sunscreen should be reapplied after prolonged swimming or vigorous activity leading to sweating.
(use water resistant or waterproof )
• Sunscreen needs to be applied liberally. Up to 1 oz(30ml) needed to cover the whole body.
Remember to apply to all areas, including the back of the neck, ears,lower lip and areas of the scalp
with thin hair.
• Clothing (tightly woven, cotton, yarn, darker clothes)- Check by seeing whether light comes through
when held up to visible light. Otherwise sunscreen may be needed under clothing or hats.
• A 4-inch wide broad-brimmed hat is required to cover the entire face and neck.

45. Teaspoon rule
To achieve application of 2 mg/cm2, the
following should be applied:
• 1 teaspoon of sunscreen to the
face/head/neck
• 1 teaspoon to each upper extremity
• 2 teaspoons total for the front and
back torso
• 2 teaspoons to each lower extremity.
• Another approach (easier and more
practica)l is to advise patients to apply
sunscreens in two coats, similar to
when painting a house.
• Advantages –
• (1) it is easier to remember
• (2) any areas that were missed the first
time around will likely be covered
• (3) an increased amount is applied
2
2

46. Recommendations for Sunscreen
Application
(3ml)
(6ml)

47. Special Patient Group Instructions
1)Photosensitive Patient
• Pt. with Photodermatoses, PMLE, taking photosensitizing drugs, or
in whom melasma or lentigines darken despite the use of sunscreens,
need better UVA protection.
• Benefit from a higher-SPF product that contains avobenzone,
ecamsule, TiO2, or zinc oxide.
• Available sunscreen agents fail to protect adequately beyond 380
nm, and physical blockers will only protect in the visible spectrum if
opaque, and not micronized.
• For PCT and other porphyria patients sensitive to visible light, only
an opaque preparation containing these pigments (as with a make-
up) will block this portion of the spectrum.

48. 2) Sensitive Skin
• A careful history of previous sunscreen
• Patients should be informed that subjective stinging in or near the eyes should not
be interpreted as a sign of true allergy.
• The patient can be instructed to perform a limited usage test (repeat open
application test) with a previously used or recommended sunscreen product.
• If true allergy is suspected, consider patch-testing
• Use chemically inert inorganic particulate materials (TiO2 or zinc oxide) as the only
active ingredients provides a suitable alternative for patients
3)Acne-Prone Patients-
• Oil-free, alcohol-based gel or a lighter-feeling cosmetic sunscreen moisturizer.
• Even an oil-free product may feel somewhat oily, as the active sunscreen
ingredients are themselves oils. The oil-free claim merely refers to the vehicle.
4)Pregnancy- for prevention of melasma
5)Children- Below 2yrs, prefer Physical sunscreen(broad spectrum, less irritation,
minimal skin penetration)

49. Sunless Tanners
• Self-tanning or sunless tanning products contain dihydroxyacetone
(DHA)
• DHA is a three-carbon sugar that reacts with the amino group of
amino acids, peptides, or proteins found in the keratin and
epidermis.
• Melanoidins are formed as a result of the Maillard or ‘browning
reaction’ in the stratum corneum
• DHA provides SPF 3 or 4 protection.
• The brown color obtained on the skin does absorb the low end of
the visible spectrum, with overlap into the long UVA, and may
provide some UVA-1 protection.
• Because the resultant color from these products can last up to
several days, patients also need to be reminded that the duration of
UV protection is more shortlived than that of the skin color change.

50. Immune Protection Factor
• IPF is the ability of sunscreen products to prevent
UV-induced immunosuppression.
• IPF is assessed by complex methods such as the
ability of a sunscreen to inhibit either the
sensitization or elicitation arm of contact or
delayed-type hypersensitivity reactions to
allergens such as dinitrochlorobenzene and
nickel, respectively.
• IPF is considered to correlate better with the
UVA protectiveness of a sunscreen than with its
SPF

51. Clothing Indices
• UPF(UV Protection factor)- measures amt of UVR that can
penetrate fabric and reach skin
• ratio of average effective UV radiation irradiance transmitted and
calculated through air to the average effective UV radiation
irradiance transmitted and calculated through a fabric
• Indicates how much longer a person can stay in the Sun when fabric
covers the skin, erythema being the endpoint
Grading of UPF:
• Good protection (UPF: 15–24);
• Very good protection (UPF: 25–39);
• Excellent protection (UPF: 40–50+).
• Fabric SPF is similar to SPF, except that fabric is used to protect the
skin while testing instead of a sunscreen.

52. New Sunscreen Technologies
SunSpheres
• SunSpheres are styrene/acrylate copolymers that do not absorb UV
irradiation but enhance the effectiveness of the active sunscreen
ingredients.
• The SunSphere polymer beads are filled with water, which migrates
out of the particle, leaving behind tiny air-filled spheres, which have
a lower refractive index (1.0) than the dried sunscreen film (1.4–
1.5).
• As a result, scattering of UV radiation occurs, increasing the
probability of contact with the active UV filters in the sunscreen.
• SunSpheres are also available in a powder form and can boost SPF
by 50–70%, making it possible to reduce the concentration of active
ingredients.

53. Microencapsulation
• Active sunscreen ingredients are entrapped
within a silica shell, as a result of which
allergic or irritant reactions to the active
ingredient can be minimized, and
incompatible sunscreen ingredients can be
safely combined without loss of efficacy.

54. Systemic Photoprotection
• Systemic sunscreens - compounds that have a systemic
photoprotective effect
• EX-
1. β-Carotene
2. Antimalarials(chloroquine, HCQ, and quinacrine)
3. Oral psoralens- 8-Methoxypsoralen (8-MOP) and
trimethyl psoralen(TMP)
4. Ascorbic acid, α-tocopherols , retinol (i.e., vitamins A, C,
and E)
5. Selenium, green tea polyphenols, PABA, antihistamines,
aspirin, indomethacin, and corticosteroids