A scientifically elegant hydrating serum that replenishes the exact moisture-retaining molecules your skin produces naturally but loses with age. It won't deliver dramatic visible results, but as the quiet infrastructure that makes your entire routine work better — especially if you use retinoids, acids, or live in dry climates — it's an under-$10 essential that punches well above its price.
Amino Acids + B5
A scientifically elegant hydrating serum that replenishes the exact moisture-retaining molecules your skin produces naturally but loses with age. It won't deliver dramatic visible results, but as the quiet infrastructure that makes your entire routine work better — especially if you use retinoids, acids, or live in dry climates — it's an under-$10 essential that punches well above its price.
Score Breakdown
A thoughtfully designed NMF-mimicking formula with near-zero irritation risk and broad suitability across all skin types. The ingredient quality reflects genuine formulation science — the amino acid profile mirrors skin biology — though the actives are hydrating rather than transformative. Exceptional value at $9.20.
Data Confidence: high
This product has been on market since 2018 with approximately 3,000+ user reviews across retailers. Panthenol and NMF components are extensively documented in cosmetic dermatology literature with strong safety and efficacy data.
0/100
Overall Score
Ingredient Quality 0
Value for Money 0
Suitability Breadth 0
Irritation Risk (↑ = safer) 0
Assessment
Pros
- Biomimetic formula with 12 amino acids at 17% mirroring skin's natural NMF profile
- Panthenol at clinically validated 5% concentration for barrier repair
- Ultra-lightweight texture absorbs instantly without residue or greasiness
- Zero known conflicts — compatible with every active ingredient
- Excellent hydration buffer for retinoid and exfoliant users
- pH within skin's natural range (4.8-5.3) minimizing disruption
- Fragrance-free, alcohol-free, oil-free, silicone-free formula
- Outstanding value at $9.20 for a multi-component hydrating serum
Cons
- Can feel sticky or tacky when more than 2-3 drops are applied
- Subtle, infrastructure-level results that lack dramatic visible impact
- Not safe for fungal-acne-prone skin due to amino acid content
- Small 30 mL bottle runs out quickly with twice-daily use
- Occasional pilling under certain foundations or sunscreens
Full Review
There's a category of skincare product that doesn't get the attention it deserves: the hydrating support serum. It's not the star of the routine — that role goes to the retinol, the vitamin C, the exfoliant. But without proper hydration, those star ingredients perform worse, irritate more, and deliver less. The Ordinary's Amino Acids + B5 exists to be the infrastructure that makes everything else work.
The concept behind this formula is biomimicry. The skin's stratum corneum retains water through a complex mixture of hygroscopic molecules collectively called the natural moisturizing factor, or NMF. Amino acids constitute approximately 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 — essentially reconstructing the NMF profile that your skin produces on its own but in diminishing quantities after your mid-twenties.
The formulation philosophy stands in deliberate contrast to the hyaluronic acid approach. Hyaluronic acid is a powerful humectant, but it's a single molecule doing one job. This serum deploys a dozen different moisture-retaining compounds that each interact slightly differently with the stratum corneum's lipid matrix and protein structures. The result is hydration that feels more integrated and less superficial — less like a wet blanket on top of the skin and more like the skin itself remembering how to hold water.
Panthenol at 5% is the anchor ingredient. Pro-vitamin B5 has one of the most robust evidence bases in cosmetic dermatology. It penetrates the stratum corneum, converts to pantothenic acid, and upregulates lipid synthesis — effectively helping the skin repair its own barrier from the inside out. A 2011 study in the Journal of Cosmetic Science found that panthenol formulations at this concentration produced significant decreases in transepidermal water loss within 30 days. A 2020 comprehensive review in Pharmaceuticals confirmed its role in accelerating re-epithelialization and restoring barrier function after cosmetic procedures.
On the skin, this serum is ghostly. It's thinner than water — almost impossibly light — with a faint slip that helps it spread evenly. Three to four drops across the face absorb within seconds. There's no scent, no tingling (the label mentions a possible mild tingle from citric acid, but most users never notice it), and no visible residue. If you weren't paying attention, you might think you hadn't applied anything at all.
That invisibility is both the product's greatest strength and its marketing challenge. In a market that rewards visible transformations and satisfying textures, a serum that feels like water and delivers results you can only measure in what doesn't go wrong is a hard sell. But dermatologists understand this category. When your retinoid doesn't flake, when your exfoliant doesn't sting, when your skin doesn't tighten in the afternoon — that's this serum doing its job.
The compatibility profile is essentially universal. The Ordinary states this product has no known conflicts with any other ingredients. That means it slots into any routine, at any step, alongside any active. It works before retinoids as a hydration buffer. It works after exfoliants as a recovery aid. It works mixed into other serums for a more comfortable application. It's the diplomatic middle child of the skincare routine — getting along with everyone and making the household run smoother.
For sensitive skin, this formula is particularly valuable. The ingredient list reads like a who's who of gentle, skin-compatible compounds. No fragrance, no alcohol, no silicones, no oils, no exfoliating acids at active concentrations. The pH sits at 4.8-5.3, which is right in the skin's natural range. If you've been looking for a hydrating serum that won't trigger reactivity, this is about as safe as it gets.
The limitations are honest and expected. This is not a transformative product. It won't brighten dark spots, smooth wrinkles, clear acne, or produce before-and-after photos that go viral on social media. If you're using it correctly, you'll notice its absence more than its presence — skip it for a few days while using a retinoid, and you'll suddenly understand what it was doing. The texture can also feel slightly sticky if you overdose; 2-3 drops is genuinely enough for the full face.
At $9.20, there's almost no reason not to try it. The only people who should pass are those with fungal acne — some amino acids can be metabolized by Malassezia yeast — and those who genuinely have all the hydration they need and want to simplify rather than add steps. For everyone else, particularly anyone using drying active ingredients or living in climates where indoor heating or air conditioning depletes ambient humidity, this is the under-$10 support player that makes the rest of your routine sound better.
Formula
Ingredients
The hero actives that drive this product's performance.
| Ingredient | Function | Evidence |
|---|---|---|
| Panthenol (Pro-Vitamin B5) (5%) | The primary active humectant in this formula, panthenol penetrates the stratum corneum and converts to pantothenic acid, enhancing lipid synthesis and barrier repair. At 5%, it works synergistically with the amino acid complex to reduce transepidermal water loss — clinical studies have shown this concentration produces significant TEWL decreases within 30 days. | well-established |
| Multi-Amino Acid Complex (17%) | Twelve amino acids — glycine, alanine, serine, threonine, valine, proline, isoleucine, lysine, histidine, phenylalanine, aspartic acid, and glutamic acid — collectively mirror the amino acid profile of the skin's natural moisturizing factor (NMF). Together they provide building blocks for keratin synthesis and support the skin's moisture retention system, creating a biomimetic hydration reservoir that declines with age. | well-established |
| Sodium PCA | The sodium salt of pyrrolidone carboxylic acid, comprising approximately 12% of the skin's natural NMF. In this formula, it acts as a powerful humectant that draws moisture into the amino acid-rich environment, amplifying the hydrating effect of the combined NMF-mimicking ingredients. | well-established |
| Betaine (Trimethylglycine) | A natural osmolyte derived from sugar beets that protects cells from osmotic stress and dehydration. In this water-based formula, it provides a secondary humectant layer that complements the NMF amino acids, helping the skin retain moisture even in low-humidity environments where traditional humectants can backfire. | promising |
| Sodium Lactate | A component of the skin's natural moisturizing factor that works as a humectant at this non-exfoliating concentration. It mirrors the lactate naturally present in the stratum corneum, reinforcing the NMF-mimicking strategy of the overall formula rather than providing any exfoliating activity. | well-established |
Full INCI List · pH 5
Aqua (Water), Propanediol, Betaine, Sodium PCA, Panthenol, Sodium Lactate, Arginine, PCA, Aspartic Acid, Glycine, Alanine, Serine, Threonine, Valine, Proline, Isoleucine, Lysine HCl, Histidine, Phenylalanine, Glutamic Acid, Citric Acid, Dimethyl Isosorbide, Polysorbate 20, Trisodium Ethylenediamine Disuccinate, 1,2-Hexanediol, Caprylyl Glycol
Product Flags
✓ Fragrance Free✓ Alcohol Free✓ Oil Free✓ Silicone Free✓ Paraben Free✓ Sulfate Free✓ Cruelty Free✓ Vegan✗ Fungal Acne Safe
Potential Irritants
Citric acid (pH adjuster, may cause mild tingling)
Compatibility
Skin Match
Best For
Works For
Not Ideal For
Addresses These Conditions
dehydration dryness compromised skin barrier sensitivity dullness post procedure
Routine Step
serum
Time of Day
AM & PM
Pregnancy Safe
Yes ✓
Layering Tips
Apply after water-based actives (vitamin C, niacinamide) and before heavier serums and moisturizers. Works beautifully as a hydration buffer applied before retinoids or after exfoliating acids. Can be mixed with other serums for simplified application.
Results Timeline
Immediate hydration and plumping on first application. Improved skin texture and reduced flakiness within 1-2 weeks. Strengthened moisture barrier and more resilient, less reactive skin after 4-8 weeks of consistent use.
Pairs Well With
Hyaluronic acidNiacinamideRetinol or retinoid treatmentsVitamin CAHAs and BHAsCeramide moisturizersPeptide serums
Sample AM Routine
- Gentle cleanser
- Vitamin C serum
- The Ordinary Amino Acids + B5
- Moisturizer
- Sunscreen
Sample PM Routine
- Cleanser
- Exfoliant or retinoid (alternate nights)
- The Ordinary Amino Acids + B5
- Moisturizer
Evidence
Science
The Science
The science behind this formula centers on the skin's natural moisturizing factor (NMF) — the complex mixture of hygroscopic substances within the stratum corneum responsible for maintaining proper hydration. Amino acids constitute approximately 40% of NMF, making them the largest single component class. Research published in Biochimica et Biophysica Acta (2010) established that NMF levels directly correlate with stratum corneum water content and barrier function, and that depletion by surfactants, UV exposure, and aging leads to measurably drier, less functional skin.
A 2024 study in the Journal of Cosmetics, Dermatological Sciences and Applications found that six key NMF amino acids peak in concentration between ages 25-29 and decline thereafter. Topical replenishment with these amino acids improved skin hydration, texture, pore appearance, wrinkles, and dullness over an 8-week period — supporting the premise that exogenous NMF supplementation can meaningfully address age-related hydration decline.
Panthenol, the formula's anchor active at 5%, has particularly robust clinical evidence. A 2011 study in the Journal of Cosmetic Science demonstrated that panthenol formulations at 1% and 5% produced significant decreases in transepidermal water loss after 30 days, with the 5% concentration showing superior results. Mechanistically, panthenol penetrates the stratum corneum, is converted to pantothenic acid, and integrates into coenzyme A — a critical cofactor for lipid biosynthesis in the skin. This process enhances the production of barrier lipids from within, rather than merely coating the surface.
A comprehensive 2020 review in Pharmaceuticals confirmed dexpanthenol's (panthenol's) efficacy in upregulating genes critical for wound healing, accelerating re-epithelialization, and restoring skin barrier function after cosmetic and medical procedures. A 2009 study in the Journal of Dermatological Treatment further demonstrated anti-inflammatory effects, showing that dexpanthenol reduced irritation after sodium lauryl sulfate challenge — directly relevant to this product's use as a buffer against irritating actives.
References
- Skin moisturizing effects of panthenol-based formulations — Journal of Cosmetic Science (2011)
- Dexpanthenol in Wound Healing after Medical and Cosmetic Interventions — Pharmaceuticals (2020)
- Dexpanthenol enhances skin barrier repair and reduces inflammation after sodium lauryl sulphate-induced irritation — Journal of Dermatological Treatment (2009)
- Natural moisturizing factors (NMF) in the stratum corneum — Biochimica et Biophysica Acta (2010)
Dermatologist Perspective
Dermatologists recognize NMF replenishment as a legitimate strategy for managing dehydrated and barrier-compromised skin. Board-certified dermatologists frequently recommend hydrating serums containing amino acids and panthenol as companion products for patients on retinoid therapy, noting that maintaining adequate stratum corneum hydration reduces the irritation and flaking that lead to treatment discontinuation. The 5% panthenol concentration in this formula aligns with the levels shown to be effective in clinical studies on barrier repair and TEWL reduction. Dermatologists also note that NMF-mimicking formulations may be particularly beneficial for patients with eczema-prone or atopic skin, where NMF levels are characteristically depleted.
Guidance
Usage Guide
How to Use
Apply 3-4 drops to clean skin after water-based active serums and before heavier treatments and moisturizer. Can be used morning and evening. Works especially well when applied immediately before retinoid treatments to buffer potential irritation, or immediately after exfoliating acids to replenish stripped NMF. Can be mixed with other water-based serums for simplified application. Use sparingly — more than 3-4 drops can leave a tacky finish. Allow 15-30 seconds to absorb before layering the next product.
Value Assessment
At $9.20 for 30 mL, this is an exceptional value for a multi-component hydrating serum with clinically validated actives. Comparable NMF-replenishing serums from medical skincare brands typically cost $30-50. The formula contains 17% amino acids and 5% panthenol — concentrations that rival or exceed those in much more expensive products. Only one size is available, which means the per-milliliter cost can't be further reduced through bulk purchasing, but the base price is already remarkably low for what the formula delivers.
Who Should Buy
Anyone using retinoids, exfoliating acids, or other drying active treatments who needs hydration support without adding weight or complexity. Particularly valuable for dehydrated skin regardless of type, sensitive or reactive skin, and anyone over 30 whose NMF levels are naturally declining. An excellent choice for dry climate or indoor-heated environments.
Who Should Skip
Those prone to fungal acne — amino acids may feed Malassezia yeast. Users who prefer minimal routines and feel adequately hydrated from their moisturizer alone. Anyone looking for visible anti-aging or brightening results — this is support infrastructure, not a transformative treatment.
Ready to try The Ordinary Amino Acids + B5?
Details
Details
Texture
Ultra-thin, clear watery liquid with very slight viscosity. Feels almost like water on skin with a subtle slip. Absorbs quickly within seconds, leaving skin hydrated without visible residue.
Scent
Fragrance-free with no discernible scent. Completely neutral.
Packaging
30 mL glass dropper bottle with standard The Ordinary minimalist white label. Recyclable materials.
Finish
lightweightnon-greasynatural
What to Expect on First Use
Immediate hydration and a noticeable plumping effect on first application. No tingling, burning, or adjustment period for most users. A mild tingling sensation may occur in some — this is noted on the product label and is attributed to the citric acid pH adjuster. Results are subtle but cumulative.
How Long It Lasts
2-3 months with twice-daily full-face application (3-4 drops per use)
Period After Opening
12 months
Best Season
All Year
Certifications
Cruelty-free (Leaping Bunny)Vegan
Background
The Why
The skin's natural moisturizing factor — a complex of amino acids, PCA, lactate, urea, and other humectants — is responsible for keeping the stratum corneum hydrated and functional. NMF levels decline with age and are depleted by surfactants, low humidity, and UV exposure. The Ordinary designed this serum to replenish those losses directly, using a multi-amino-acid profile that mirrors the skin's own NMF composition rather than substituting a single synthetic humectant.
About The Ordinary Established Brand (5–20 years)
The Ordinary launched in 2016 under DECIEM and rapidly became one of the most recognized clinical skincare brands globally. Its ingredient-first, transparency-driven approach is backed by formulation science, though the brand does not conduct proprietary clinical trials on most products.
Brand founded: 2016 · Product launched: 2018
Myth vs. Reality
Myths
Myth
Amino acids in skincare are just a marketing gimmick — they can't actually hydrate skin.
Reality
Amino acids constitute approximately 40% of the skin's natural moisturizing factor and are directly responsible for water retention in the stratum corneum. A 2024 study found that six key NMF amino acids peak at age 25-29 then decline, and topical replenishment improved skin hydration, texture, and dullness over 8 weeks.
Myth
This serum is basically just a watered-down version of a regular moisturizer.
Reality
This product works through a fundamentally different mechanism than occlusive moisturizers. It replenishes the hygroscopic (water-attracting) molecules within the stratum corneum itself, while moisturizers primarily work by trapping moisture on the skin's surface. The two approaches are complementary, not redundant.
FAQ
FAQ
What does The Ordinary Amino Acids + B5 do for skin?
This serum replenishes the skin's natural moisturizing factor (NMF) — the cocktail of amino acids and humectants within the stratum corneum responsible for water retention. With 17% amino acids mirroring the skin's own NMF profile and 5% panthenol for barrier repair, it strengthens the skin's ability to hold moisture from within rather than just coating the surface.
Can I use The Ordinary Amino Acids + B5 with retinol?
Yes — this is one of its best uses. Applied before retinol or retinoid treatments, it acts as a hydration buffer that reduces the dryness, flaking, and irritation that retinoids commonly cause. The amino acids and panthenol support barrier function without interfering with retinoid activity.
Is The Ordinary Amino Acids + B5 the same as hyaluronic acid?
No. While both are hydrating serums, they work through different mechanisms. Hyaluronic acid is a single humectant molecule that draws water to the skin's surface. This serum contains twelve amino acids and multiple NMF components that integrate into the stratum corneum's own moisture-retention system. The two products are complementary and can be used together.
When should I apply The Ordinary Amino Acids + B5 in my routine?
Apply after cleansing and any water-based active serums (vitamin C, niacinamide, alpha arbutin), but before heavier serums, moisturizers, and oils. It works as a hydration layer that preps the skin for subsequent products. Use 3-4 drops and allow 15-30 seconds to absorb before the next step.
Is The Ordinary Amino Acids + B5 safe during pregnancy?
Yes. This serum contains amino acids and panthenol — both are naturally occurring in the body and have no known risks during pregnancy or breastfeeding. It appears on multiple pregnancy-safe skincare guides. Always confirm with your healthcare provider for individual guidance.
Why does The Ordinary Amino Acids + B5 feel sticky?
A slight tackiness can occur if too much product is applied. Use only 3-4 drops for the full face and allow 15-30 seconds for absorption before layering the next product. The amino acids and humectants create a hydration film that should become imperceptible once a moisturizer or sunscreen is applied on top.
Is The Ordinary Amino Acids + B5 fungal acne safe?
No. Some amino acids in this formula — particularly arginine — may be metabolized by Malassezia yeast in the presence of lipids, potentially exacerbating fungal acne. Those prone to Malassezia folliculitis should choose a different hydrating serum.
Community
Community
Common Praise
"Super hydrating — skin feels plump and moisturized immediately"
"Extremely lightweight formula that feels like water on skin"
"No conflicts with any other products — layers into any routine"
"Excellent buffer when used alongside retinoids or exfoliating acids"
"Great value at under $10 for a biomimetic hydrating serum"
"Suitable for even very sensitive and reactive skin types"
Common Complaints
"Can feel sticky or tacky if more than 2-3 drops are applied"
"Occasional pilling under makeup if too much product is used"
"Subtle results — some users feel it doesn't do anything noticeable"
"Small 30 mL bottle runs out quickly with twice-daily full-face use"
"Rare reports of breakouts in acne-prone users"
Appears In
best serum for dehydration best serum for sensitive skin best hydrating serum for retinoid users best budget hydrating serum best serum for compromised skin barrier
Related Conditions
dehydration dryness compromised skin barrier sensitivity dullness post procedure
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