BUTTER-C
Signature ingredients
Lactic acid serum OEM/ODM manufacturing
Lactic Acid Serum · Signature Ingredients · OEM/ODM
Lactic acid is sometimes called “milk acid”, but the industrial raw material is made by fermenting carbohydrates or by chemical synthesis (PubChem). It is an alpha hydroxy acid (AHA) with a slightly larger molecule than glycolic acid (90.08 versus 76.05) and mixes completely with water, which suits a water-based serum. AHA products shed the surface layer of corneocytes and help skin feel smoother; how strongly depends on the type of acid, concentration, pH and product base (FDA). Lactic acid also has moisture-related data: on human skin, lotions with the L form raised stratum corneum ceramides by 48% and the DL form by 25%. Human evidence at home-use concentrations comes from small trials from the 1990s, including a 22-week randomized double-blind trial in 74 women assigned to an 8% L-lactic acid cream, an 8% glycolic acid cream or the vehicle cream — the two AHA creams were judged “modestly useful” by the authors themselves; the studies used creams and lotions, and the sources checked contain no trial in serum form. AHAs also make skin more sensitive to UV during use. That is why, in ASEAN, lactic acid shares Annex III entry A6 with glycolic acid: skin products for general use may contain at most 10% calculated as the acid, the finished product must be pH 3.5 or higher, and the label must carry a sunburn warning from 2.5% when the product contains no sunscreen. The lactic acid serum Butter-C develops starts from three numbers — the acid content of the raw-material solution, total AHA calculated as acid, and finished-product pH — before skin feel. Butter-C offers turnkey OEM/ODM manufacturing, from formula development to a labeled finished product and its notification dossier.
Formula base
Lactic acid at the center, buffer and serum base built around pH
A serum is almost all water, so nothing in the base masks the lactic acid. The raw-material solution, neutralizer, thickener and humectants are chosen together, because all four decide the finished product's pH and skin feel.
Lactic acid — the named ingredient
INCI Lactic Acid; C3H6O3, molecular weight 90.08; L form (CAS 79-33-4) or DL (CAS 50-21-5); pKa about 3.86 at 20 °C (PubChem). Butter-C's standing raw material is a “Lactic Acid (and) Water” solution — the formula percentage is converted to pure acid using the certificate of analysis (COA) for each lot, and the label lists both Lactic Acid and Water. The COA should state L or DL: on human skin, an L-form lotion raised stratum corneum ceramides by 48%, DL by 25%, and D caused no change (Rawlings 1996, authors from a company research laboratory). The concentrated solution causes skin irritation and serious eye damage (GHS classification on PubChem) — safety glasses and gloves when weighing.
Neutralization and lactate buffer
Sodium Hydroxide partly neutralizes the lactic acid to reach the target pH; Sodium Lactate is added so the acid–salt pair keeps pH from drifting. Lactate salts still fall under entry A6 and count toward the total calculated as acid — 1% anhydrous sodium lactate corresponds to about 0.80% lactic acid (90.08 / 112.06). Sodium lactate is also usually supplied as a solution, with its concentration taken from the COA. Neutralization lowers free acid, not the “total”.
A serum base that tolerates acid pH
Carbomer loses viscosity at low pH and with a lot of lactate salt (an electrolyte) — Hydroxyethylcellulose, Xanthan Gum or Sclerotium Gum are used, with viscosity checked at the formula's actual pH. Glycerin, Betaine and Sodium Hyaluronate help skin feel less tight and dry. Panthenol and Allantoin are added only when finished-product pH is set at 4 or above and monitored in stability testing, as on the mandelic acid serum page. No fragrance, and no retinoid or BHA in the same bottle.
Preservation and acid-resistant packaging
Phenoxyethanol (max 1.0% — Annex VI Ref 29) with Ethylhexylglycerin; a low pH does not replace challenge testing. Dark glass bottle with an acid-resistant dropper gasket, or an acid-resistant plastic pump bottle; avoid metal parts that are not acid-resistant. Bottle, gasket and dropper are soaked with the sample in the stability study on the actual commercial pack.
Key technical points
Four numbers and one warning to settle first
Two serums both labeled “lactic acid 5%” can act on skin very differently. The points below decide efficacy, comfort and whether the notification dossier holds up.
From raw-material solution to total AHA
Annex III entry A6 covers “Glycolic and lactic acid, their common salts and simple esters”: skin products for general use “≤ 10% total when calculated as the acids”. The total includes lactic acid, any glycolic acid, the salt formed on neutralization and any added Sodium Lactate. The amount of raw-material solution is worked back from the COA — as an illustration, a lot stating 85% acid needs about 5.9% solution for 5% lactic acid. The label states the acid percentage, not the solution percentage.
Finished-product pH and free acid
Finished-product pH must be “≥ pH 3.5”. With a pKa of about 3.86, the share of lactic acid in free form, estimated with the Henderson–Hasselbalch equation, is about 70% at pH 3.5, about 42% at pH 4.0 and about 19% at pH 4.5 (a calculation, not a measurement). Raising pH makes the product gentler but reduces exfoliation; choosing pH balances effect, stinging and stability of the base.
A serum is not a cream
FDA notes that a cosmetic-type cream base lets AHAs penetrate deeper than a simple solution — a change of base means irritation must be reassessed. Human data for lactic acid come from an 8% cream (Stiller 1996), a 5% lotion (Rogers 1989) and a 5% versus 12% study (Smith 1996; 12% already exceeds the 10% limit for general-use products in ASEAN). The sources checked contain no trial in serum form, so the serum level is fixed through stinging and tolerance testing on the finished product itself.
UV sensitivity and the warning
In a double-blind controlled trial in 29 people, 10% glycolic acid at pH 3.5 (a representative AHA, not lactic acid) applied for 4 weeks increased sunburn cells and lowered the UV dose causing redness; the effect was gone one week after stopping (Kaidbey 2003). Annex III footnote (13): “Labeling mandatory for products containing Glycolic and/or Lactic acids at a concentration ≥ 2.5% and do not contain a sunscreen. Not required for products that are intended to be applied to non sun exposed areas of the body, contain a sunscreen or a lower concentration of AHA.” Face serums usually contain no sunscreen, so from 2.5% the warning must be printed. Butter-C includes lactate salts (converted to acid) when comparing with the 2.5% threshold — a cautious reading that needs regulatory confirmation.
Three formulation directions
Three ways to put lactic acid into a serum
Lactic acid serum with a lactate buffer
Lactic acid partly neutralized, Sodium Lactate to limit pH drift, a thin Hydroxyethylcellulose gel base with Glycerin and Betaine. Total A6 no more than 10% calculated as acid; the exact level is set through stinging and tolerance testing, with reference to 5% (Smith 1996) and the 8% cream (Stiller 1996). For normal and rough, dry skin already used to actives. The label carries the sunburn alert.
Low-strength lactic acid serum for beginners
Total A6 below 2.5% (including salts converted to acid — a cautious reading), with a richer humectant base of Sodium Hyaluronate and Panthenol. Below the footnote (13) threshold the warning is not mandatory, but FDA (USA) still recommends a sunburn alert on cosmetics containing AHAs — Butter-C suggests keeping the sunscreen advice. The sources checked have no human efficacy data at this level; claims stop at supporting moisture and light smoothing, to be tested on the finished product.
Lactic acid – gluconolactone serum
Adds Gluconolactone as on the PHA toner page: it is not covered by entry A6, but it slowly hydrolyzes to gluconic acid and makes pH drift — pH is readjusted once the system has equilibrated and followed in stability testing. Lactic acid still counts against the A6 limit and the 2.5% threshold as in the other two directions. The word “gentle” goes on the label only after stinging and tolerance testing on the finished product itself.
How this differs from other AHA pages
The AHA toner uses glycolic acid in a thin liquid; the AHA body lotion uses lactic acid over the large skin area of the body; the mandelic acid serum uses an AHA outside entry A6. This page is for lactic acid on the face in serum form: conversion from the raw-material solution, the lactate buffer, L versus DL, and lactic acid's own moisture-related data.
Parameters we monitor
What our R&D team measures on every sample
Below are the parameters Butter-C monitors during formula development and scale-up. Specific limits are agreed with you on the approved sample and then written into the product's in-house specification.
- Incoming raw-material documents
- COA of the lactic acid solution for each lot: acid content, L or DL form; COA of the sodium lactate solution if used — inputs to the A6 total calculation.
- pH
- Measured directly at 25 °C on every batch; the in-house pH range has a margin above the mandatory 3.5. pH drift monitored at each stability time point.
- AHA content
- HPLC assay of lactic acid (and glycolic acid if present) at the start and after stability testing; the A6 total calculation as acid, including salts, kept on file.
- Sensory, clarity & viscosity
- Color, odor, clarity; viscosity measured at the formula's actual pH at each stability time point — polymers can thin over time in an acid medium.
- Stability
- Accelerated aging at 40 °C, freeze–thaw cycling and light exposure; pH, AHA content, color and viscosity monitored.
- Packaging compatibility
- Filled into the exact bottle, gasket, dropper or pump to be used; deformation, material odor and signs of corrosion on metal parts monitored.
- Microbiology & preservative challenge
- Tested at a GLP / ISO 17025-accredited laboratory; preservative efficacy (challenge) test per ISO 11930 — a low pH does not replace the preservative system.
- Stinging & irritation
- Tested on volunteers, including facial stinging; the basis for fixing concentration and pH before mass production.
- Label check
- Total AHA, pH and the sunburn alert checked against Annex III entry A6 before the label artwork is approved.
Claims
Claims within the cosmetic scope
Much of the literature on lactic acid concerns 30–92% peels performed by physicians, or 12% ammonium lactate lotion used in studies of moderate to severe dry skin; the tyrosinase-inhibition data come from cell experiments (Usuki 2003). Marketing copy slips into that language easily, while Annex 03-MP of Circular 06/2011/TT-BYT does not accept drug-like claims. Under Annex III, above 10% up to 20% is for professional use and above 20% is for qualified medical practitioners only — outside the scope of a retail serum. Below is the wording Butter-C suggests.
Gently exfoliates, helps the skin surface feel smoother
Instead of: peels the skin, skin renewal, “at-home peel”, “works like a peel”.
Supports moisture retention, helps skin feel less rough and dry (to be tested on the finished product)
Basis: L- and DL-lactic acid lotions raised stratum corneum ceramides and improved barrier function (water loss measured after an SLS challenge) and resistance to dry skin (Rawlings 1996); note that a 5% lactic acid lotion reduced dryness less than a 12% ammonium lactate lotion (Rogers 1989). Instead of: “restores the skin barrier”, “72-hour deep hydration”, wording that mentions skin diseases.
Helps skin look less dull (to be tested on the finished product)
Supported by the 8% L-lactic acid cream trial: on the forearms, the cream reduced sallowness, mottled pigmentation and roughness versus the vehicle cream after 22 weeks (Stiller 1996); for a serum it must be tested on the finished product. Instead of: whitening, fades dark marks, removes melasma, “blocks melanin”.
Contains lactic acid, with a percentage
A percentage is stated only when it is the total calculated as the acid and matches the assay; pH may be stated alongside. Instead of: the percentage of raw-material solution, percentages with no stated basis, figures above 10% on retail products.
Mandatory warning
Verbatim from Annex III: “Sunburn alert: This product contains an alpha hydroxy acid (AHA) that may increase your skin’s sensitivity to the sun and particularly the possibility of sunburn. Use a sunscreen, wear sun protective clothing, and limit sun exposure while using this product and for a week afterwards.” The local-language label carries an equivalent translation approved by regulatory review. Instead of: “does not cause sun sensitivity”, dropping the warning because the rest is “only salt”.
Directions and label cautions
Use in the evening, start every other day and patch-test a small area first; use sunscreen during the day while using the product and for a week after stopping; do not use on broken skin, after shaving or hair removal, or on sunburned skin; avoid the eye area; use retinol, BHA and other AHAs at a different time; stop if redness or burning persists. Sensitive or redness-prone skin: start at a low concentration. Pregnancy: insufficient data, ask a doctor. Instead of: suitable for all skin types, safe during pregnancy.
Manufacturing specifications
Current capabilities
- Texture
- Clear, thin or slightly thickened gel serum, colorless; body from acid-tolerant polymers.
- Pack format
- Dark glass dropper bottle with an acid-resistant gasket, or acid-resistant plastic pump bottle. Volume agreed when packaging is selected.
- Minimum order quantity
- Agreed per order — depends on the formula direction and pack format.
- Testing
- Tested at a GLP / ISO 17025-accredited laboratory, with AHA assay and pH on every batch; certificate of analysis delivered with each batch.
- Dossier
- Product Information File (PIF) and cosmetic product notification dossier prepared by Butter-C, including the A6 total AHA calculation from the raw-material COA and stinging and irritation test results.
- Packaging
- Label design, printing and packing run in parallel with formula development; the sunburn alert is laid out from the first label draft.
Suggested product concept
Lactic acid serum with a lactate buffer for normal and rough, dry skin
One product direction to help you picture the result — not a ready-made product for sale. The actual formula is built around your brand's positioning and price range.
Lactic acid partly neutralized, pH around 4
The named ingredient; total A6 (including sodium lactate converted to acid) no more than 10%, the exact level fixed through stinging and tolerance testing; converted from the raw-material solution's COA.
Glycerin, Betaine, Sodium Hyaluronate
Humectants paired with the acid; a Hydroxyethylcellulose base keeps the body at low pH.
No fragrance, no alcohol, no BHA or retinoid
A short ingredient list so lactic acid is the clear lead and tolerance is easy to assess.
30 ml dark glass dropper bottle
Acid-resistant gasket; label with the sunburn alert, directions for evening use and daytime sunscreen.
Customization options
What you can specify
The same product type can serve very different customers. Tell us your requirements in the areas below and our pharmacists will build the matching formula.
Sales channel and concentration
Retail: total max 10%, pH from 3.5. Above 10% up to 20% is a professional-use product (pH from 3.0, label “For professional use only”); the channel must be set before development.
L or DL form
Choose a supplier that states the form on the COA; the L form showed a larger ceramide increase in the Rawlings 1996 study.
pH and stinging
The closer the pH is to 3.5, the more free acid and the more likely stinging; raising pH makes the product gentler but reduces the effect.
Co-acids
Lactic acid alone, with glycolic acid (sharing the A6 limit) or with gluconolactone (outside A6) — this decides how the total is calculated and the label wording.
Humectants and soothing agents
Glycerin, Betaine, Sodium Lactate, Sodium Hyaluronate, Panthenol, Allantoin — chosen according to finished-product pH.
Ingredient direction
Alcohol-free, fragrance-free, paraben-free, vegan — please tell us at the start so we can choose suitable raw materials.
Further reading
Related topics
Lactic acid in cosmetics
Mechanism, evidence, the ASEAN 10% and pH 3.5 limits, sun sensitivity (in Vietnamese).
Sodium lactate in cosmetics
Lactate buffers, conversion to acid and free-acid share by pH (in Vietnamese).
Glycolic acid in cosmetics
An AHA in the same A6 entry, with a smaller molecule than lactic acid (in Vietnamese).
UVA, UVB, visible light and the skin
Why AHA users need sun protection during and after use (in Vietnamese).
AHA glycolic acid toner OEM/ODM
Same A6 entry, in toner form for the face.
Lactic acid AHA body lotion OEM/ODM
Lactic acid over the large skin area of the body.
Mandelic acid serum OEM/ODM
A larger-molecule AHA outside entry A6.
How we work
From idea to finished batch
Eight steps and three milestones signed off by both sides: approved sample, notification number, finished batch. Step-by-step details →
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