Citric acid is an alpha-hydroxy acid that often pops up in many skincare formulations—as well as everything from food to cleaning products. Derived from, you guessed it, citrus fruits, it offers a wide variety of benefits when used in all of these different capacities.
Citric Acid for Hair
Type of ingredient: Alpha-hydroxy acids
Main benefits: Lowers the pH of haircare products, which can help improve not only how well the formula functions but also how hair looks, says Isfahan Chambers-Harris, MD.
Who should use it: This is a safe ingredient for everyone to use, as it optimizes the performance and safety of products, says cosmetic chemist Laua Lam-Phare. However, it should be avoided by those who have a citrus allergy, cautions Chambers-Harris.
How often can you use it: Daily
Works well with: Most other ingredients, hence its prevalence in many different types of cosmetic formulations across both the skincare and haircare categories.
Don't use with: Our experts were unaware of any ingredients known to interact negatively with citric acid in haircare products.
Citric acid is often found in haircare formulas, too, though here it's largely used for formulation purposes, thanks to its ability to alter a product's pH. Here, Laura Lam-Phare, a cosmetic chemist in West Hollywood, CA, and Isfahan Chambers-Harris, MD, a trichologist and founder of Alodia, explain more.
Meet the Expert
Benefits of Citric Acid for Hair
This is all goes back to that good ol' pH scale. As a quickie reminder (and in case you skipped pH day in high school chemistry class), the pH scale goes from 0 to 14: 0 is the most acidic, 7 is neutral, and 14 is the most alkaline. For reference, citric acid has a natural pH of about 2, and is an excellent pH balancer. What exactly does that mean? "When used in proper concentrations in manufactured haircare products, it lowers their pH to an ideal level," says Chambers-Harris. Healthy hair falls within the pH range of 4.5–5.5, but many of the haircare products that we use daily (we're looking at you, shampoos) have a much higher, more alkaline pH. In this case, the citric acid helps lower that, she explains.
But what does that translate to when it comes to how your hair looks and feels? Too alkaline of a pH tends to open up the cuticle, the outermost layer of the hair, which essentially looks like shingles on a rooftop. When these "shingles" are open, your strands appear dull, frizzy, and rough, not to mention that moisture can escape and leave hair dryer, too. Keeping your hair at that optimal pH helps keep the hair cuticles sealed. This means they can better hold in moisture and reflect light so that hair looks healthy and shiny, says Chambers-Harris. There are some benefits for the scalp, too. Maintaining that target pH of 4.5–5.5 helps prevent microbes from growing on the scalp, she adds.
And haircare benefits aside, the right pH is also important for a product's function. "With the use of citric acid, the formulation can be optimized to a specific pH to ensure product performance and product safety," points out Lam-Phare.
Hair Type Consideration
Both experts we spoke with underscore that any hair type can benefit from citric acid, which is why it's used in all types of products and is such a common ingredient.
How to Use Citric Acid for Hair
There's nothing really specific you need to worry about or consider when it comes to citric acid in haircare. The ingredient is found in all kinds of products, probably many that you're already using on the regular; in other words, it's not one of those super-functional, highly active ingredients you need to go seeking out, nor worry about avoiding, says Lam-Phare.
The only two caveats: One, Chambers-Harris advises avoiding it if you have a citrus allergy. Two, don't go trying to buy straight-up citric acid online and attempting any kind of DIY experiment. Citric acid needs to be used in specific and correct concentrations in order to be safe and effective, she cautions.
Why Is Citric Acid So Common in Haircare Products?
Citric acid helps lower the pH in many products, such as shampoo, that have much higher, more alkaline pH levels. This helps keep hair at healthy pH levels.
What Hair Types Can Benefit From Citric Acid?
Both experts we spoke with underscore that any hair type can benefit from citric acid—which is why it's found in so many haircare products.