Why vitamin C serums come in dark bottles. Expert decodes the science | Lifestyle News

“Vitamin C degrades much faster in the presence of light. The ultraviolet rays react with ascorbic acid and make the reaction much faster. As a result, it becomes inactive and will not be effective.”If you’ve ever bought a vitamin C serum, you’ve probably noticed that most come in amber, brown or other dark-coloured bottles. While it may look like a branding choice, the packaging has a scientific reasoning behind it.What looks like a “dark aesthetic” product is actually an attempt to prevent it from being damaged. Dr Saurabh Arora, Managing Director, Auriga Research, tells that light is one of vitamin C’s biggest enemies.
Vitamin C degrades much faster in the presence of light. The ultraviolet rays react with ascorbic acid and make the reaction much faster. As a result, it becomes inactive and will not be effective. That’s why vitamin C serums, much like several medicines, are usually sold in amber or dark-coloured bottles. “This is a very basic protection that is needed from light…. It is definitely required,” he explains.
DISCLAIMER: This article is based on information from the public domain and/or the experts we spoke to. Always consult your health practitioner before starting any routine.
Vitamin C and oxidation process
If the serum is exposed to air,  oxygen reacts with vitamin C and break it down (Ai generated image)
However, light isn’t the only factor that affects the ingredient. Because vitamin C is an antioxidant, it also reacts easily with oxygen in the air. As Dr Arora explains, as your serum comes in contact with the oxygen, the degradation begins, and light helps fasten this reaction.
“So, it is very important to control both these things,” he says. A dark glass bottle and a tightly sealed dropper help slow this process limiting exposure to light and air.Story continues below this ad
But don’t we open the lid to use the serum? Does it degrade then? So if you open a dropper bottle repeatedly, the air exposure does not degrade your serum.
“No, they do not make it less effective if the dropper has proper sealing and you close it properly. There should be no problem there because this is the most common format used for vitamin C serums,” Dr Arora says
He further adds that manufacturers conduct stability and in-use studies to ensure the packaging performs well under normal use, and that all vitamin C serums should ideally come in dark bottles, irrespective of the concentration.
“When we develop the formulation, we do stability studies in these packs. We even do in-use stability studies to understand how the product will behave when the consumer is using it. So, this packaging is optimised for that, and it is not a concern.”Story continues below this ad
Is good packaging the only criteria you need to check
Packaging alone doesn’t determine whether a serum is good. “The formulation is also very important: how it has been made, which form of vitamin C has been used, how much water is there, and whether it is aqueous-based or not. The formulation actually plays a more important role, but yes, packaging is equally important.”
When choosing a serum, Dr Arora recommends checking what form of vitamin C has been added. “For example, if it is a water-based serum and you add ascorbic acid, it will go bad. For an aqueous system, you have to use magnesium ascorl phosphate.”
As per the expert, ascorbic acid comes in various forms — magnesium ascorl phosphate, ethyl ascorbic acid, sodium ascorbate and tetrahexyldecyl ascorbate. All of these have different stability profiles, and a well-formulated serum often contains a combination of these.

If you can check the label, look at the ingredient l and see which form of ascorbic acid is there (Image: Freepik)
How to know that your serum has gone bad
If your vitamin C serum starts turning yellow or brown, it could be a sign that it is oxidising.Story continues below this ad
“Vitamin C serum will gradually turn darker and darker, and it is a clear indication that the ascorbic acid, or vitamin C, is breaking down. So, it is not a good sign.”
A slight colour change during regular use can be expected, but if the serum is already dark when you open it or changes colour very quickly, it may no longer be effective.
Lastly, Dr Arora recommends storing your vitamin C serum bottles in the same way you store your medicines: “Keep them in a cool, dry place so that they do not break down. ”
DISCLAIMER: This article is based on information from the public domain and/or the experts we spoke to. Always consult your health practitioner before starting any routine.