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| | Sunscreen Ingredients :
Finding protection for UVA, UVB and visible light.
People with photosensitivity can be sensitive to UVB, UVA, visible and even
infrared light (as described on the Sunscreens web
page).
To achieve protection across a wide range, sunscreen makers may include several different sunscreen ingredients.
Most commercial sunscreens protect in the UVB region, but UVA protection is
not so good. As seen in Table 1,
many sunscreen ingredients do not fully protect in the UVA range. For example,
if the main active ingredient in a sunscreen is PABA, you can see in Table
1 that PABA only protects up to 313 nm. The PABA only sunscreen would leave you
unprotected in the UVA range from 313 to 400 nm. For full protection for both UVA and UVB, sunscreen ingredients
need to protect in wavelengths from 290 to 400 nm. Sunscreen
ingredients that do protect better in the UVA range include:
-
Avobenzone (Parsol 1789) (320-400 nm) To be effective in a sunscreen
avobenzone must be combined with another ingredient to make avobenzone
photostable.
- Mexoryl SX (290-400 nm) (available only in Canada and Europe)
- Mexoryl XL (290-400 nm) (available only in Europe)
- Micronized zinc oxide (290-380 nm),
Another misunderstanding by many doctors is that zinc oxide and titanium
dioxide sunscreens protect against the entire spectrum. Today, only micronized
titanium dioxide and zinc oxide are used in sunscreens because they are
transparent. Micronized versions of titanium dioxide only protects
in the UVB range, and and zinc oxide protects in the UVB and UVA
range. In the past, large particle size zinc oxide and titanium dioxide
was used in white opaque sunscreens used on life guards noses or in diaper rash
ointment. If large particle size zinc oxide and
titanium dioxide are used in sunscreens, they must be tinted or colored to
achieve a flesh tone, or they will be blindingly white. For people with
visible light sensitivity, these old fashioned ingredients can provide
protection across the entire spectrum, UVB, UVA, visible and infrared light.
Figure 1: Solar spectrum of light
TABLE 1: Protection wavebands of sunscreens (Based on
table by [Bissonnette])
| Sunscreens |
Wavelength
protection (nm) |
Maximum
Estimated
PPD |
| Chemical
sunscreens |
|
|
| Aminobenzoic
acid and derivatives |
|
|
| – |
PABA |
260-313 |
|
| – |
Lisadimate (Glyceryl PABA) |
264-315 |
|
| – |
Padimate O |
290-315 |
|
| – |
Roxadimate |
280-330 |
|
| Anthranilates |
|
| – |
Menthyl anthranilate |
260-380 |
|
| Benzophenones |
|
| – |
Dioxybenzone |
250-390 |
|
| – |
Oxybenzone |
270-350 |
|
| – |
Sulisobenzone (Eusolex 4360) |
260-375 |
|
| Camphor
derivatives |
|
| – |
Benzoate-4 methylbenzylidene
camphor |
290-300 |
|
| – |
Mexoryl SX |
290-400 |
15b |
| – |
Mexoryl XL |
290-400 |
28b |
| Cinnamates |
|
| – |
Octocrylene |
250-360 |
|
| – |
Octyl methoxycinnamate (Parsol
MCX) |
290-320 |
|
| Dibenzoylmethanes |
|
| – |
Avobenzone (Parsol 1789) |
320-400 |
Note c |
| Salicylates |
|
| – |
Homosalate |
295-315 |
|
| – |
Octyl salicylate |
280-320 |
|
| – |
Trolamine salicylate |
260-320 |
|
| Others |
|
| – |
Phenylbenzimidazole |
290-340 |
|
| - |
Octyl triazone [Uvinul] |
290-330 |
|
| Physical
sunscreens |
|
|
| - |
Titanium dioxide (micronized)
used in most sunscreens today |
290-320 |
|
| - |
Zinc oxide (micronized) used
in most sunscreens today |
290-380 |
8 or 9b |
| – |
Titanium dioxide (large
particle size, opaque) white stuff -1960s lifeguards used to put on
their noses. No longer used in modern sunscreens.a
See Visible light sunscreens. |
290-700 |
|
| – |
Zinc oxide (large particle
size, opaque) white stuff -1960s lifeguards used to put on their
noses. No longer used in modern sunscreens.a
See Visible light sunscreens. |
290-700 |
|
a Large particle size zinc oxide and titanium dioxide
are no
longer used in modern sunscreens because they are opaque and very white
(like diaper rash ointment). If large particle size zinc oxide and
titanium dioxide are used in sunscreens, they must be tinted or colored to
achieve a flesh tone because they do cover the skin. For people with
visible light sensitivity, these old fashioned ingredients can provide
protection. But sunscreens with these ingredients are rare. See Visible
light sunscreens.
b [Nora80] Estimated PPD. This
ingredient may be combined with other ingredients to achieve the estimated PPD.
But this ingredient is the crucial ingredient needed to achieve the high PPD
value.
c Avobenzone (Parsol 1789) is an excellent UVA
ingredient, but by itself, avobenzone is unstable. To be effective in a
sunscreen avobenzone must be combined with another ingredient to make avobenzone
photostable.
References
[Bissonnette] Update on sunscreens. Robert Bissonnette. Skin Therapy Letter Volume 2, Number 5.
1997. [http://www.skintherapyletter.com/download/stl_7_7.pdf]
[Nora80] (Estimated PPDs of sunscreens) http://www.makeupalley.com/user/notepad/nora80/ [Uvinul]
Uvinul grades: UV absorbers for cosmetic products, November 1998 http://www.suppliercd.com/scd10/BASF0001/Attach/m0002297.pdf
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