If your skin darkens then it means that it tries to protect itself (naturally) against UVR. So the sunscreen does not protect fully. Though no sunscreen have 100% photo-protection! An SPF 30 (when applied the right amount) will protect 98% against UVB. If you apply less then 2 mg/cm² then you will have much less protection (see the post above).
It can also be that the ZnO has smaller particle size (which is difficult to believe since it seems to be a "natural" sunscreen) and the UVA protection is weak hence the tanning of your skin.
It might be that the UV index is very high (higher than normal that has been this year on the North Hemisphere) and/or you are in the sun for longer periods of time.
The worst case is that the measurements of the sunscreen were not correct and it is wrongly labelled. (It should have a lower SPF value. (In the BASF sunscreen simulator it gives SPF 12.5, PPD 9.6; but this is valid for larger particle size ZnO and the real measurements (Colipa) of each sunscreen that will determine its labelled SPF. Of course these measurements are not real life measurements and don't take into account the surface of the skin etc. So while a sunscreen gives high SPF values in the lab might not perform so well in real life. The skin surface is uneven -while the surface used for testing is even- hence the importance of film-formers in sunscreens).
Hey eva, why would Devita solar protection spf 30 darken someone in the sun if it contains 19% zinc as its active just like burnout (which doesn't cause darkening)?
Is it possible something can protect you while giving some color at the same time?
ACTIVE INGREDIENT: Zinc oxide 19%. INACTIVE INGREDIENTS: Aloe barbadensis (certified organic aloe vera gel), Purified Water (aqua), Capric/caprylic triglycerides (derived from coconut oil), Glycerin (vegetable), Hyaluronic acid (vegan source), Glyceryl stearate SE (derived from vegetable oil), Stearic acid, Lecithin phospholipid, Tocopherol (vitamin E), Allantoin, Vitis vinifera (grape) seed extract. Ingredient labeling adheres to international INCI standards.
So you don't think that something can both slightly darken and protect at the same time? Could any of the other ingredients be interfering with the zinc oxide absorption? This is an extremely light sunscreen for what it purports to be. Also, burnout seems to prevent darkening without re-application.
It's probably related to the dispersion of the zinc oxide particles in the sunscreen.
It may be a generalization, but I think the physical sunblock particles such as ZnO are not evenly dispersed in organic/natural sunscreens. They clump, settle, etc., and are hard to redisperse since sunscreen fluid is usually thick and viscous, so even a good vigorous shake might not do the trick (Realizing the innuendos here. Please forgive. Cant think of a rephrase).
I have become a believer, as far as sunblocks go, in less is more if the product is made by Neutrogena, Olay, Coppertone, or one of the more established brands:
That is, 10% zinc oxide in a Coppertone sunblock is far more protective than 25% in an organic brand.
I guess they are just better at making them, with decades of experience, formulating them, and thus develop the recipe with all the concerns of sun protection in mind, whereas organic companies mix a few 'organic' bases and slap in/on the zinc oxide and voila, sunblock is born.
That is a radical simplification, of course, but seems to be the trend.
This only applies to sunscreens, which require knowledge and experience to formulate effectively, and not at all to foods and other health products, where organic is usually, though not always, best.
[And, to mention in a follow up edit: There are reports from Consumer Reports and the FDA and a bunch of other sources that may suggest otherwise, but the problem is the people who conduct these tests just don't 'get it'. One needs to be a true heliophobe to be attuned enough to measure the effect of a sunblock, and to measure how well it endures heat, abuse, expiration, etc. So, reports that suggest otherwise should be viewed with suspicion, since I usually find big problems with the way they go about testing each sunblock. They are doing it in the "I want to go to the beach and want my sunscreen to protect me from burning and Ill reapply it every few hours". These people are not counting every UV beam that hits them. That is why the reports are so skewered. And, I could be wrong, but there is a major bias toward natural/organic products in the cosmetic/health industries, and with good reason, so there could be a placebo effect on testers who are not genuinely attuned to the effects of sun on their skin and are more looking for overall impressions. I know because I have tried so many types of sunscreens and find the 'brand names' more effective, since I look closely at my face and am definitely aware when the sun has affected me. Wow, that was a long rant. Sorry!]
Edited by Brafarality, 16 June 2012 - 07:10 PM.
(UVR will do that much faster). It is only relevant when you create a product (mix ingredients so they stay together for a longer period of time, f.ex. storing in a bottle).
