BUTTER-C
Signature ingredients
Salicylic acid BHA shampoo OEM/ODM manufacturing
Salicylic Acid Scalp Shampoo · Signature Ingredients · OEM/ODM
Salicylic acid — BHA — is familiar to oily-skin users from facial toners and serums; on the scalp it is used to help loosen the layer of horny flakes so the shampoo can wash them away together with sebum. Shampoo is the product type with the highest ceiling in ASEAN Annex III: Ref 98 item (a) “Rinse-off hair products”, a maximum of 3.0% — one and a half times the 2.0% for toners or body washes — counting every use of salicylic acid including any used as a preservative, and not for use in preparations for children under three. A high ceiling does not mean high efficacy: shampoo sits on the scalp for a few minutes before rinsing, from pH 5 upward only about 1% of the salicylic acid remains as free acid (calculated from pKa 2.98), and the human data we found on salicylic acid shampoos mostly involve formulas combining it with other actives. Claims therefore stop at cleansing hair, scalp and loose flakes; to claim “cleanses dandruff”, add an anti-dandruff active or assess the finished product itself. Butter-C offers full-service OEM/ODM manufacturing, from cleansing system, pH selection and tolerance testing to a labeled finished product with its cosmetic product notification.
Formula base
Salicylic acid in a rinse-off shampoo base
This page differs from our anti-dandruff shampoo page in that salicylic acid is the lead character rather than one option on a list of actives: raw material form, pH, total amount under Ref 98 and the young-child warning decide the rest of the formula.
Salicylic acid (Salicylic Acid)
Synthetic crystalline raw material, CAS 69-72-7, molecular weight 138.12; water solubility about 2.24 mg/mL at 25 °C (≈0.22%), readily soluble in alcohol and glycols; pKa 2.98. Shampoo falls under item (a) “Rinse-off hair products” of Annex III Ref 98: a maximum of 3.0% in the ready-for-use product — higher than the 2.0% (item b) that applies to BHA toners, BHA body washes and leave-on scalp serums.
Cleansing system
Sodium Laureth Sulfate with Cocamidopropyl Betaine for oily scalps; Decyl Glucoside, Coco-Glucoside with betaine for the sulfate-free version. Acyl amino acid systems are sensitive to low pH — they can turn hazy, precipitate or change viscosity — so they are not the default; if you want to keep them, pH is set from a pH–clarity–viscosity curve of the formula itself.
Solvent, pH adjustment, buffer
Propanediol or Butylene Glycol to dissolve salicylic acid before it enters the base; Sodium Hydroxide for partial neutralization; Sodium Citrate – Citric Acid to hold pH. The part neutralized to salicylate still counts toward the 3.0% total.
Hair conditioning, preservation, chelation
Guar Hydroxypropyltrimonium Chloride, Polyquaternium-10, Panthenol restore softness because users often wash several times a week; Sodium Benzoate (rinse-off max 2.5% as benzoic acid — Annex VI Ref 1) or Phenoxyethanol (max 1%); Disodium EDTA because salicylate forms a color with iron ions.
Key technical points
Four things specific to a shampoo named after BHA
A BHA shampoo is not a BHA toner poured into a shampoo bottle: contact time, the pH of the shampoo base and lather running into the eyes change the whole problem.
Count the total under Ref 98, item (a)
Ref 98 states “These levels are inclusive of any use of salicylic acid” and “As a preservative, see Annex VI, Part 1, No 3”: add the free acid, the part neutralized to salicylate, the part converted from betaine salicylate (factor 0.541 — a cautious reading pending regulatory confirmation) and any part used as a preservative (Annex VI Ref 3, max 0.5% as acid). The 3.0% level applies only to rinse-off hair products: a 2-in-1 body & hair wash also used on the body still takes the 2.0% level (item b), as on our BHA body wash page (cautious reading).
Rinse-off and pH: the share that acts is small
A measurement-method study (author from an ingredient supplier, Davies 2015) states in its objective that only about 1–2% of the total salicylic acid stays on the skin during face washing. With pKa 2.98, the un-ionized share is about 9% at pH 4.0, 3% at pH 4.5, 1% at pH 5.0 and 0.3% at pH 5.5 (calculated from pKa for dilute aqueous solution, not measured in a surfactant-rich base). Lowering pH raises the free acid but challenges cleansing-system stability and mildness to eyes and scalp — pH is set together with tolerance testing, not taken as a default number.
Salicylate is a negatively charged electrolyte
Fully neutralizing 2.0% salicylic acid with NaOH releases sodium ions equivalent to about 0.85% NaCl (calculated from molar masses), shifting the salt curve: viscosity is adjusted after the BHA level and pH are fixed (formulation experience). Positively charged hair-conditioning polymers (Guar Hydroxypropyltrimonium Chloride, Polyquaternium-10) are compatibility-tested for clarity and precipitation on dilution (formulation experience).
Young children, eyes, no sprays
Ref 98: “Not to be used in preparations for children under three years of age”; the label line “Not to be used for children under three years of age” is mandatory for products that might be used for children under three (footnote 8: “Solely for products which might be used for children under three years of age”). Shampoo sits in a shared family bathroom, so Butter-C recommends always printing this line (pending regulatory confirmation). The “except for shampoos” exemption in Annex VI Ref 3 covers only salicylate salts used as preservatives, not salicylic acid used as an active. Lather easily runs into the eyes: eye-irritation screening and an eye-avoidance line. Ref 98 forbids applications that may lead to inhalation — no BHA dry-shampoo sprays.
Three formulation directions
Three ways to put BHA in a shampoo bottle
BHA shampoo for oily scalps, sulfate–betaine base
Salicylic acid dissolved first in glycol, then partly neutralized; rich foam, quick rinse; for oily, flaky scalps and hot, humid climates. Claims stop at cleansing hair, scalp and loose flakes.
BHA shampoo combined with an anti-dandruff active
Salicylic acid paired with Piroctone Olamine as in the Loden & Wessman trial (2000, authors from industry): a 0.75% piroctone olamine + 2% salicylic acid shampoo and a 1% zinc pyrithione shampoo (randomized, double-blind, half-head comparison, 19 people, washing twice a week for almost 4 weeks) both clearly reduced dandruff. That is a result for the combination, not separable for salicylic acid. Piroctone olamine appears only in Annex VI Ref 35 (rinse-off 1%, marked (+)) — the level as an active needs regulatory confirmation; see the anti-dandruff shampoo page.
Gentle sulfate-free BHA shampoo
Decyl Glucoside, Coco-Glucoside with betaine, moderate salicylic acid, plenty of conditioners, fragrance-free, for frequent washing. The alkyl glucoside group is a recognized contact allergen — complete INCI list; “gentle” only when the finished product has been tolerance-tested.
Packaging is designed with the formula
Opaque, light-blocking plastic pump or flip-cap bottles (salicylic acid gradually discolors in sunlight); no spray heads. Plastics, gaskets and pumps are soak-tested with the acid–surfactant solution.
Parameters we monitor
What our R&D lab measures on every sample
Below is the set of parameters Butter-C monitors while developing the formula and transferring it to production. Specific limits are agreed with you on the approved sample and then written into the product’s in-house specification.
- pH
- Measured directly at 25°C on every batch and at each stability checkpoint; pH sets the free acid, viscosity and preservative performance at the same time.
- Salicylic acid content
- HPLC assay at release and at stability checkpoints; expressed as total salicylic acid (including salt, converted and preservative portions) against the 3.0% limit.
- Viscosity & clarity
- Rotational viscometer at 25°C; salt curve built after neutralization, because salicylate is also an electrolyte.
- Crystallization at low temperature
- Held at 4°C and through freeze–thaw cycling; checked for crystals at the bottom and neck of the bottle and in the pump.
- Foaming
- Foam height and stability by a standard method, against the approved sample.
- Stability & color
- Accelerated aging at 40°C, freeze–thaw and light exposure; monitored for discoloration (iron ions, light), separation, odor change and pH drift.
- Eye irritation & scalp tolerance
- Eye-irritation screening using the method the testing laboratory proposes; tolerance testing on volunteers before pH and salicylic acid level are fixed — the basis for CIR’s “formulated to be non-irritating and non-sensitizing” condition.
- Microbiology & preservative challenge
- Tested at a GLP / ISO 17025-accredited laboratory; preservative efficacy (challenge) test to ISO 11930 at the finished-product pH.
- Human assessment (if claimed)
- Scalp flake scoring before and after a washing course at an independent testing facility, when you want to state “reduces visible flakes” or a figure.
- Packaging compatibility
- Filled into the actual bottle and pump; monitored for pump clogging, gasket discoloration and plastic deformation.
Claims
Writing claims within the cosmetic scope
People buying a BHA shampoo often think of dandruff, itch and thick scaly patches — among which seborrheic dermatitis, scalp psoriasis and scalp ringworm are conditions a dermatologist must diagnose. Verified data on salicylic acid shampoos are limited: in an old double-blind trial (Leyden 1987, 48 people with moderate to severe scalp scaling, washing twice a week for 5 weeks), a 2% sulfur + 2% salicylic acid formula reduced scaling and shed corneocyte counts more than either ingredient alone or the shampoo base; the abstract does not report whether 2% salicylic acid alone differed from the base. So a cosmetic shampoo stops at cleansing and softening loose flakes.
Cleanses hair, scalp and loose flakes
Instead of: dandruff claims beyond cosmetic scope, “removes dandruff permanently”.
Helps soften and loosen flakes on the scalp
Only when assessed on the finished product itself, since a shampoo is rinsed off within minutes. Instead of: keratolytic, peels away scales, claims about thick scaly patches of scalp conditions that need a dermatologist.
Cleanses dandruff, reduces visible flakes
Only when the formula contains an anti-dandruff active (e.g. Piroctone Olamine) or the finished product has been assessed on people. Instead of: claims about an effect on scalp microorganisms, “dandruff gone for good”.
For oily, flaky scalps
Describes the scalp type. Instead of: controls oil, reduces sebum production — salicylic acid’s sebaceous data so far come only from cultured sebocytes (Lu 2019).
Contains salicylic acid (BHA)
State the amount only when an assay proves it and every source of salicylic acid has been added up. Instead of: figures above 3.0% once betaine salicylate is added, “peel strength”.
Directions and label warnings
“Not to be used for children under three years of age” (Ref 98, footnote 8; Butter-C recommends always printing it on shampoo — pending regulatory confirmation). Avoid the eyes and rinse with plenty of water if lather gets in; do not use on scratched or irritated scalp; do not stack several salicylic acid products; stop if stinging persists. A red, very itchy scalp, thick spreading scales or patchy hair loss should be seen by a dermatologist. Instead of: for the whole family including babies, safe in pregnancy, claims about hair loss or hair growth.
Manufacturing specifications
Capabilities
- Texture
- Clear or slightly opaque shampoo; sulfate–betaine or glucoside–betaine base.
- Pack formats
- Opaque plastic pump or flip-cap bottles; no spray heads. Volume agreed when packaging is selected.
- Minimum order quantity
- Agreed per order — depends on the BHA form, cleansing system and pack format chosen.
- Testing
- Tested at a GLP / ISO 17025-accredited laboratory, including salicylic acid assay; certificate of analysis supplied with every batch.
- Dossier
- Product Information File (PIF) and cosmetic product notification prepared by Butter-C, including the total salicylic acid calculation under Annex III Ref 98 and the under-three warning on the label.
- Packaging
- Label design, printing and packing run in parallel with the formula.
Suggested product concept
Fragrance-free BHA shampoo for oily, flaky scalps
One product idea to help you picture the line — not a ready-made product for sale. The actual formula is built around your brand’s positioning and price range.
Salicylic acid
The named ingredient; level and pH set by tolerance testing and eye-irritation screening, total salicylic acid no more than 3.0% (Annex III Ref 98, item a). The shampoos in both verified studies used 2% salicylic acid; the headline results reported are for the combined formulas.
Sodium Laureth Sulfate, Cocamidopropyl Betaine
Rich foam, removes excess oil, rinses fast; viscosity adjusted with salt after BHA level and pH are fixed.
Guar Hydroxypropyltrimonium Chloride, Panthenol
Hair stays soft, not dry, with frequent washing; compatibility with salicylate checked by clarity on dilution.
400 ml opaque plastic pump bottle
Light-blocking; label states “Not to be used for children under three years of age”, eye avoidance and how to lather on the scalp and rinse.
Customization options
What you can specify
The same product type can serve very different customers. Tell us what you want in each area below and our pharmacists will build the formula to match.
BHA form
Crystalline salicylic acid or betaine salicylate — decides how it is dissolved, how the limit is converted and the label wording.
Salicylic acid level and pH
Stronger or milder versions are two different concentration–pH pairs, set by tolerance testing and eye-irritation screening.
Cleansing system
High-foam sulfate–betaine or sulfate-free glucoside–betaine; acyl amino acid systems need separate testing at acidic pH.
Combinations
Piroctone Olamine if you want a dandruff-cleansing claim (see the anti-dandruff shampoo page); menthol for a cooling feel (see the peppermint shampoo page) — adds eye sting, so tolerance testing is redone.
Fragrance
Fragrance-free, or light herbal or citrus scents stable at acidic pH; fragrance is also a source of contact allergy. ASEAN annexes have no list of fragrance allergens that must be named; for EU export, name them above 0.01% (rinse-off) under EU rules.
Product set
Shampoo with a scalp serum: a leave-on serum may contain at most 2.0% salicylic acid (Ref 98, item b) and must not be bottled as a spray; using several salicylic acid products adds up exposure — directions go on the label.
Further reading
Related knowledge
Salicylic acid (BHA) in cosmetics
Mechanism, evidence, ASEAN Annex III limits and safety notes (in Vietnamese).
Anti-dandruff shampoo OEM/ODM manufacturing
General page: anti-dandruff actives, where salicylic acid is one option that helps loosen flakes.
Dandruff and oily scalp
Telling dandruff apart from seborrheic dermatitis, psoriasis and scalp ringworm, and when to see a dermatologist (in Vietnamese).
Salicylic acid BHA body wash OEM/ODM manufacturing
Same active used on the body: 2.0% ceiling, also 2.0% for a 2-in-1 body & hair wash.
Salicylic acid BHA toner OEM/ODM manufacturing
Leave-on for the face: its own solvent system, pH and tolerance testing.
Scalp serum OEM/ODM manufacturing
Leave-on scalp product: salicylic acid max 2.0%, no spray format.
Betaine salicylate in cosmetics
The 0.541 conversion factor and why “gentle BHA” is still limited evidence (in Vietnamese).
Peppermint & menthol shampoo OEM/ODM manufacturing
When you want to add a cooling feel: total menthol, eye sting and the young-child warning.
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 (in Vietnamese) →
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