Azelaic acid: the three types and how to use it with retinol

Azelaic acid dominated skincare conversations this summer, and not for a good reason. An online sleuth read the ingredient list of a popular Korean azelaic acid serum and found sodium hydroxide, also known as lye, right below the active. That sparked an argument that ran for months: if a brand raises the pH of the formula, is the acid still working, or have shoppers been sold a useless product? Board certified dermatologist Shereene Idriss walks through what is actually going on, and the short version is that three different products share the name azelaic acid while only one matches the studies everyone keeps citing.

The three types of azelaic acid

Free or suspended form

This is the original, the version the research has used for years, and the one Idriss has referred to for the past five years. The Ordinary sells it for about 12 dollars. It works, but it feels like gritty speckle because the acid sits on the skin as fine particles rather than dissolving. That texture is the reason many people quietly abandon the product, and a formula that peels off your face and rolls into a drawer gives you none of the benefit.

Ionized form

Here the brand nudges the pH up, often with sodium hydroxide, so the acid dissolves. The result is the watery, cosmetically elegant Korean style serum found in lines like Medicube or Anua, the kind that has never really peeled. This is the version that set the internet on fire. The fear was that a fully ionized acid cannot get into the skin. A 2012 study showed the opposite: dissolving azelaic acid first in the right vehicle can actually improve how much of it helps, and across different pH levels and formulas the active stays effective. What matters is the whole formulation, not the ingredient in isolation, so buying an ionized serum is not a scam.

The derivative: potassium azeloyl diglycinate

This one is not azelaic acid at all. It is a water soluble derivative that helps with redness, oil production and uneven tone, and it feels pleasant on the skin. The real scandal of the summer was labeling: one brand sold a product marketed as a 10% azelaic acid product that actually contained only this derivative, with no azelaic acid in it, then quietly changed the name. Correcting the name was the right move, but customers had spent years buying something other than what they thought.

Idriss is transparent that she formulates her own option, a reducer serum with 5% azelaic acid and 5% of the derivative, a 10% complex with no percentage claim on the box.

The internet complaints, one by one

• The itch. The prescription insert mentions it: the first 10 to 20 minutes can itch. It usually settles within 2 to 3 weeks. Persistent burning is a reason to stop.
• It wrecked my barrier. Azelaic acid is not an exfoliating acid or a retinoid, so it does not break the barrier down. Dig into most of these stories and another product, often a retinoid, is the cause.
• The purge panic. Azelaic acid cannot purge skin because it does not push anything to the surface. New breakouts point to a different irritant.
• The prescription lottery. Two people with the same 15% prescription can have opposite experiences because generics come from different manufacturers, A, B or C, each of which formulates a little differently. You can ask your pharmacy for a version from another manufacturer.

How to layer it with a retinoid

• Ionized form or derivative (type 2 or 3): apply at night, then your tretinoin or retinol on top, no waiting.
• Free form (The Ordinary or prescription): apply to damp skin, let it sit for a minute or two, then the retinoid, so it absorbs.
• Frequency: azelaic acid is gentle enough for nightly use and you do not need to earn it. The retinoid is the one you earn, so start at two nights a week, such as Tuesday and Thursday, rather than every night.
• Test first: run azelaic acid alone for several nights with a plain moisturizer, or even petroleum jelly, before adding anything harsher.

If you bought the wrong bottle

Nothing is wasted. Redness or oily skin does well with the derivative. Stubborn melasma or pigmentation needs a prescription at 15% or higher, since that is the strength shown to help with stubborn pigment. Pustular, inflamed breakouts that did not respond to a pharmacy formula are worth a second try with a different manufacturer, or a visit to a dermatologist for something systemic rather than topical.

Bottom line

The ionized form drama was aimed at the wrong target: it is safe and it works. The argument worth having was about a derivative being labeled as azelaic acid. Pick the form that matches your goal, apply it before your retinoid, and keep the schedule simple.