Amino Acids + B5

Hydrating support serums often lack attention. They aren’t the stars like retinol, vitamin C, or exfoliants. But without hydration, those ingredients perform worse, irritate more, and deliver less. The Ordinary’s Amino Acids + B5 provides the infrastructure to make everything else work.

This formula uses biomimicry. The skin’s stratum corneum retains water using hygroscopic molecules called the natural moisturizing factor, or NMF. Amino acids make up about 40% of NMF. Sodium PCA accounts for about 12%. Lactate, urea, and various ions make up the rest. This serum contains twelve amino acids at 17% total concentration, sodium PCA, sodium lactate, and 5% panthenol. It reconstructs the NMF profile the skin produces, which diminishes after your mid-twenties.

This formulation differs from the hyaluronic acid approach. Hyaluronic acid is a powerful humectant, but it is a single molecule. This serum uses twelve different moisture-retaining compounds that interact differently with the stratum corneum’s lipid matrix and protein structures. The hydration feels integrated rather than superficial—less like a wet blanket and more like the skin itself holding water.

5% panthenol is the anchor ingredient. Pro-vitamin B5 has robust evidence in cosmetic dermatology. It penetrates the stratum corneum, converts to pantothenic acid, and upregulates lipid synthesis to help the skin repair its barrier from the inside out. A 2011 study in the Journal of Cosmetic Science found that panthenol formulations at this concentration decreased transepidermal water loss within 30 days. A 2020 review in Pharmaceuticals confirmed it accelerates re-epithelialization and restores barrier function after cosmetic procedures.

Texture

This serum is ghostly on the skin. It is thinner than water and very light, with a faint slip for even spreading. Three to four drops absorb across the face within seconds. There is no scent, no tingling (the label mentions a possible mild tingle from citric acid, but most users never notice it), and no visible residue. You might not even feel it applied.

Common Praise

This invisibility is the product’s greatest strength and its marketing challenge. In a market rewarding visible transformations, a serum that feels like water and delivers results measured by what doesn’t go wrong is a hard sell. But dermatologists understand this category. When your retinoid doesn’t flake, your exfoliant doesn’t sting, or your skin doesn’t tighten in the afternoon, The Ordinary’s Amino Acids + B5 is doing its job.

Pairs Well With

The compatibility profile is universal. The Ordinary states this product has no known conflicts with other ingredients. It slots into any routine, at any step, alongside any active. It works before retinoids as a hydration buffer, after exfoliants as a recovery aid, or mixed into other serums for more comfortable application. It is the diplomatic middle child of the skincare routine that makes the household run smoother.

Best for

This formula is valuable for sensitive skin. The ingredient list uses gentle, skin-compatible compounds. It has no fragrance, no alcohol, no silicones, no oils, and no exfoliating acids at active concentrations. The pH is 4.8-5.3, which matches the skin’s natural range. If you want a hydrating serum that won’t trigger reactivity, this is as safe as it gets.

Not ideal for

The limitations are expected. This is not a transformative product. It won’t brighten dark spots, smooth wrinkles, clear acne, or produce viral social media photos. If used correctly, you notice its absence more than its presence—skip it for a few days while using a retinoid and you will see the difference. The texture can feel slightly sticky if you use too much; 2-3 drops is enough for the full face.

Who Should Buy

At $9.20, there is little reason not to try it. Only those with fungal acne should pass, as some amino acids can be metabolized by Malassezia yeast, or those who already have sufficient hydration and want fewer steps. For everyone else—especially those using drying actives or living in climates with indoor heating or air conditioning—this is an under-$10 support player that makes your routine work better.