You’ve just cracked open a fresh bottle of lactic acid serum to add to your skincare routine and you’re suddenly greeted by a funky sour milk smell. If you’ve never used lactic acid before, your first thought may be toss it in the trash, but wait! This is not necessarily always a red flag. Here’s why these serums can naturally have a sour scent:
What does Lactic Acid Smell Like?
The Ordinary Lactic Acid 10% + HA is many skincare junkie’s first introduction to lactic acid and many skincare beginners are surprised by the tart scent of this popular AHA. Lactic Acid naturally has a light sour acidic scent that may bring to mind fermented dairy products like yogurt or sour cream.
Lactic acid is actually naturally produced by our bodies and is released via sweat glands especially after a heavy workout session. Lactic acid is one of the many reasons your workout clothes sometimes smell sour after a bout of intense exercise. 1
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Are Lactic Acid Serums Supposed to Smell?
Different grades of lactic acid used in skincare will have varying levels of scent. Some serums will have an extremely strong acidic scent while other formulations will not have a noticeable smell. The Ordinary actually reformulated their wildly popular Lactic Acid 10% + HA serum back in 2017 to use a grade of lactic acid that reportedly has no odor.
If your skincare product initially had no scent and then further down the road starts to develop a sour or musty smell it has likely spoiled. Skincare formulas can acquire funky smells as the formula breaks down, or if it is exposed to dirt/bacteria. You should throw away any products that suddenly start to smell strange or if the texture changes out of the blue.
Formulas with Vitamin C are one of the most common situations in which you’ll see color and scent changes. You can learn more about why this happens here: Why did my Vitamin C Serum Turn Yellow?
If your lactic acid serum has gone bad and you’re in the market for a new one, I do highly recommend the tried and true The Ordinary Lactic Acid 10% + HA. I’ve gone through 4+ bottles of this serum and it has done wonders for my acne-prone dry skin and it seems to be a very stable formula as well.