The Formulation Nightmare of Pure Azelaic Acid
Pure azelaic acid is a symmetrical 9-carbon saturated dicarboxylic acid that forms tight crystalline lattices with a melting point above 106°C.
To incorporate 10% to 20% into a cosmetic product, formulators must either suspend micronized solid particles in heavy silicone/wax bases (resulting in gritty, matte creams like The Ordinary's Azelaic Acid Suspension) or use aggressive glycols.
These dense vehicles can cause pilling under sunscreen and induce sensory tingling upon application.
Potassium Azeloyl Diglycinate (PAD): The Glycine Conjugate
PAD is created by reacting azelaic acid with two molecules of the amino acid glycine and neutralizing with potassium hydroxide.
This chemical modification yields a clear, stable, 100% water-soluble liquid ingredient that can be effortlessly formulated into crystal-clear, ultra-lightweight watery toners and hydrating serums (such as Geek & Gorgeous aPAD).
Because of the attached glycine molecules, PAD provides intrinsic humectant and skin-elasticity benefits alongside oil control.
Clinical Efficacy: Prescription Evidence vs. Cosmetic Studies
While PAD has demonstrated clinical efficacy in reducing sebum secretion and calming rosacea redness at 3% to 6% concentrations (Azeclair trials), it lacks the four decades of FDA-approved randomized controlled trials supporting pure 15%–20% Azelaic Acid for papulopustular rosacea and severe melasma.
For severe inflammatory rosacea pustules, pure Azelaic Acid remains the gold standard; for daytime elegance, sensitive skin, and oily T-zones, PAD is an exceptional non-pilling alternative.
Takeaway: If you need maximum clinical power for severe rosacea or melasma and can tolerate a thicker cream, use pure 15% Azelaic Acid. If you want a non-pilling, lightweight watery serum that controls oil and soothes mild redness, choose Potassium Azeloyl Diglycinate (PAD).