1. Sunscreens
By Yay
January 23, 2006

2. Protoprotection of skin
1. Absorption of light by chemical sunscreens;
UVB and UVA absorbers
2. Reflection and scattering of light by physical
sunscreens; Tio2 and Zno
3. Quenching of reactive O2 free radicals;
Antioxidants, Vit-C, Vit-E, B-carotene
4. Physical blocking of light; Hats, parasols,
clothing, tightly fabrics
5. Other approaches sunless tan; DHA, DAG, Tan
accelerators

3. Ultraviolet lights
 UVC 100-280 nm, all absorbed by ozone.
 UVB 280-320 nm, partially absorbed by
ozone and clouds but blocked by
windows.
 Chief cause of sunburn
 UVA 320-400 nm, passes through ozone,
glass and clouds

6. Evolutions
 UV-absorbing molecules were explored in early
20th’s in the US, Australia and Europe.
 Red petrolatum, US military employed during
World war II, which stimulated widespread in
development of suncreens after the war.
 Commercial sunscreens improved over the next
30 years, significant number of users in the mid-
1970s

7. Sun protective factor [SPF]
Minimal erythematous dose [MED]
= amount of UV radiation needed for an
individual to just start to redden.
SPF= MED (with sunscreen)
MED (without sunscreen)
Ex. A person who burns in 0.5 hr would
develop erythema in 2 hrs with an SPF 4
sunscreen (0.5 x4)
SPF primarily measures UVB, not UVA!!!

8. SPF calculation based on 2 mg/cm2 but most users
apply 0.5-1.0 mg/cm2, leaving them with an SPF
20-50% of the labeled SPF
 SPF 8 MAY ABSORB MORE THAN 88% OF INCIDENT UVB
RADIATION
 SPF 15 MAY ABSORB MORE THAN 92% OF INCIDENT
UVB RADIATION
 SPF30 MAY ABSORB MORE THAN 96.7% OF INCIDENT
UVB RADIATION
 SPF 40 MAY ABSORB MORE THAN 97.5% OF INCIDENT
UVB RADIATION

9. Mechanism of sunscreen action
1. Scattering; Physical sunscreens

10. Mechanism of sunscreen action
2. Absorption; Chemical sunscreens

12. FDA Sunscreen Final Monograph Ingredients
Drug Name Concentration, % Absorbance
Aminobenzoic acid Up to 15 UVB
Avobenzone 2-3 UVAI
Cinoxate Up to 3 UVB
Dioxybenzone Up to 3 UVB, UVAII
Ensulizole Up to 4 UVB
Homosalate Up to 15 UVB
Meradimate Up to 5 UVAII
Octocrylene Up to 10 UVB
Octinoxate Up to 7.5 UVB
Octisalate Up to 5 UVB
Oxybenzone Up to 6 UVB, UVAII
Padimate O Up to 8 UVB
Sulisobenzone Up to 10 UVB, UVAII
Titanium dioxide 2 to 25 Physical
Trolamine salicylate Up to 12 UVB
Zinc oxide 2 to 20 Physical

13.  UVB chemical sunblock sunscreen
ingredients
Cinnamates, octyl
methoxycinnamate (OMC),
Ethylhexyl p-Methoxycinnamate
 Salicylates, octyl salicytate (OCS)
 Para-aminobenzoic acid, PABA
Padimate-O, Octyl dimethyl paba
Octocrylene
Zinc oxide
Titanium Dioxide

14. CINNAMATES
 Derivatives of Cinnamon, their primary protective range is
found in the UVB range (290-320 nm).
Octyl methoxycinnamate (280-310 nm)
Cinnoxate (270-328)
 ADVANTAGES : They do not stain, non comedogenic,
widely used.
 DISADVANTAGES : Poor water resistance (frequent
reapplications), high incident of contact irritation, may
cause cross reaction allergy in persons allergic to Balsam
of Peru, tolu balsam, coca leaves, cinnamic oil.

15. SALICYLATES
 Their primary protective range is found in the
UVB range (290-320 nm).
 Homosalicylate (290-315 nm)
Octyl salicylate (260-310)
Triethanolamine salicylate (269-320)
 DISADVANTAGES : Octyl and triethanolamine
may cause photocontact dermatitis more
frequently than homosalicylate, so they are used
less frequently.

16. PABA and PABA Esters
 Their primary protective range is found in the
UVB range (290-320 nm).
 PABA (260-313 nm)
Padimate O (290-315)
Padimate A (290-315)
Glycerol aminobenzoate (260-315)
 ADVANTAGES : Water and perspiration resistant.
DISADVANTAGES : Contact and photocontact
allergy (PABA > Esters), PABA stains (Esters
stain rarely).

17. UVA chemical sunblock
sunscreen ingredients
 Oxybenzone, benzophenone,
benzophenone-3
 Avobenzone, Parsol 1789
 Zinc oxide
 Titanium Dioxide

18. Physical sunblock ingredients –Reflect or
scatter UVB, UVA and visible light, non-
irritating, non-allergenic
 Zinc oxide – recognized as a mild
antimicrobial, wound healing and sunscreen
agent. Primarily absorbs UVA light rather than
scattering or reflecting, non-irritating, non-
comedogenic, and micronized by forming many
small micro particles for cosmetic use.
 Titanium dioxide – highly reflective white
chalky mineral, non-irritating, non-comedogenic,
micronized by forming many small micro
particles for cosmetic use.

19. BENZOPHENONES
 Their primary protective range is found in the
UVA range (320-400 nm).
 Oxybenzone (270-350 nm)
Dioxybenzone (206-380)
Sulisobenzone (250-380)
 ADVANTAGES : Less allergenic than PABA, do
not stain.
DISADVANTAGES : Less water resistant than
PABA (so their bases in the sunscreens are
thicker and less cosmetically acceptable).

20. DIBENZOYLMETHANES
 The best UVA protectors, their protective range
is found in the UVA range (320-400 nm). They
offer no protection from UVB.
 Tert-butylmethoxydibenzoylmethane (310-
400 nm)
4-Isopropyldibenzoylmethane (310-400)
 DISADVANTAGES : Although isopropyl-DBM has
been used in Europe for several years, it has not
been approved for use in the USA, because of
the high incidence of contact dermatitis
reactions.

21. OTHER SUNSCREEN AGENTS
 Methylanthranilate (200-380) : With
low-level broad spectrum coverage, is
added to many sunscreens to augment
protection.
 Octocrylene (287-323)
 Etocrylene (296-383)

22. Sunscreen Efficacy
from prospective, controlled trials in human
 Reduction in the number of Actinic keratoses.
 Less incidence of cutaneous SCC.
 Preventing the development of melanocytic nevi.
 No direct evidence to prevent melanoma.
 Short term study- prevented many biochemical
measure of sun-damage but long term study is
still lacking in wrinkle prevention.

23. Self-tanning agents
 Stainers (dihydroxyacetone)
 Bronzers (dyes)
 Tan accelerators (tyrosine and psoralens)
 Solaria (sunbeds and sunlamps)

24. Dihydroxyacetone (DHA)
 Colourless 3-carbon sugar, approved by FDA
 Mostly 3-5% of DHA in self-tanning preparations
 React with amino acids only in stratum corneum layer producing
an orange-brown color (melanoidins) without any exposure to
damaging sunlight.
 Melanoidins usually apparent within an hour of application.
Maximal darkening may take 8-24 hours to develop and will last
5-7 days with a single application. Same colour can be
maintained with repeat applications every 1 to 4 days.
 Must be stressed that an overall sun protection program is still
very necessary because DHA do not protect the skin against the
sun.
 Clinical uses in vitiligo, camouflage of leg spider veins, or
possibly as protection for individuals with certain photosensitivity
disorders.
 Side effects; Contact dermatitis but rarely.

25. AAD's recommendations for
effective sunscreen use:
 Wear a broad-spectrum sunscreen with SPF of
at least 15.
 Use sunscreens every day if you are going to
be in the sun for more than 20 minutes.
 Apply sunscreens to dry skin 15 to 30 minutes
before going outdoors.
 When applying sunscreen, pay particular
attention to the face, ears, hands and arms, and
generously coat the skin that is not covered by
clothing.

26.  One ounce of sunscreen, enough to fill a shot
glass, is considered the amount needed to cover
the exposed areas of the body completely.
 Reapply sunscreens every two hours or
immediately after swimming or strenuous
activity.
 In addition to wearing a broad-spectrum
sunscreen with an SPF of 15 or higher, a
comprehensive sun protection program includes
avoiding deliberate tanning with indoor or
outdoor light, seeking shade, wearing protective
clothing, and limiting exposure during peak
hours.