Question 1

doesn't this contain propylene glycol and isn't that antifreeze?

Accepted Answer

The short answer is yes and no. Propylene Glycol is something that can be used to either prevent something from freezing or change the temperature at which something freezes and it is part of a group of substances which can do that, BUT I believe you’re thinking about the kind of anti-freeze commonly used in vehicles, the one which we're all warned against drinking because it can be poisonous to humans and many pets. That substance is Ethylene glycol not propylene glycol and ethylene glycol is considered poisonous because unlike propylene glycol which is either excreted from the body in urine or turned into lactic acid (something our bodies have no problem processing), when our bodies try to process ethylene glycol it starts to affect the central nervous system and can ultimately result in kidney failure (from the buildup of compounds the kidney can’t effectively process) and ultimately death.

Propylene Glycol is generally considered safe for human consumption and exposure up to certain limits, but if you consume too much or are allergic to it then you could have an adverse reaction. For more information here’s what the CDC has to say about the extent to which propylene glycol could ever be a problem:
 https://www.atsdr.cdc.gov/phs/phs.asp?id=1120&tid=240

And here’s a great basic discussion about the differences between Propylene and Ethylene glycol and the science around the safety of propylene glycol:
https://www.healthline.com/nutrition/propylene-glycol#section4

Question 2

Why is the serum I received yellowish brown when it should be clear?

Accepted Answer

I’ve experienced the same change in color of my vitamin C serum. My skin anesthetist said vitamin C turns yellow over time when it’s exposed to heat and light because it begins to crystalize. I asked her if the color change indicates a loss of potency. She said there is no consensus but most experts consider any loss in potency insignificant compared to the benefits of using the serum.

Question 3

Okay. There are two 20% C-Serums. What is the difference between Professional C-Serum 20% and Medical Professional Serum 20%?

Accepted Answer

One serum contains 4% hydroquinone and the other doesn't, however this one is advertised as containing it but when I received my shipment nowhere on the ingredients was it listed. For the extra price it should have had what I was paying for. It will go back, if I wanted just the 20% C I could have gotten it for $20.00 cheaper. Hopefully this was just a shipping error and not the seller it's self. Since I won't know for sure I am getting a refund. On the products themselves, I have used both serums and they are very nice, the one I wanted is better, gets rid of sun spots and really makes your skin glow.

Question 4

I have mature very oily skin. Does it make your skin oily and break-out?

Accepted Answer

Hi There, this is not oily, it is a water based serum that absorbs into the skin.

I would gradually add it into your skincare routine to avoid irritation being that it is a medical grade 20% vitamin C.

Item model number	50539
Product Dimensions	5.31 x 3.89 x 10.16 cm; 90.72 g
ASIN	B00F6XZZMY

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Obagi Medical Obagi Professional-C Serum, 1 fl. oz.

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