Hair Care Product Testing: Shampoo and Conditioner Checklist

Shampoos, conditioners, masks, oils and styling products look simple, but they are among the most heavily used cosmetics in the world, and they touch the scalp, the eyes and the skin of the whole body in the shower. Proper hair care product testing is how a brand proves that its formula is safe, stable and well preserved before it reaches a bathroom shelf. This checklist explains what to test, what the EU rules expect and what is special about hair products.

The short answer

Every hair care product sold in the EU needs a safety assessment signed by a qualified assessor (the CPSR) built on real data. For most shampoos and conditioners that means stability testing, microbiological quality testing and a preservation efficacy (challenge) test, with a patch test when you want to claim skin or scalp tolerance. Hair colours, straighteners and relaxers add stricter ingredient rules and warnings. The exact test list depends on the formula, the pack, the intended users and the claims.

Why hair products need their own approach

Hair products are used often, in warm, wet bathrooms, and are opened and closed with wet hands. That is the perfect environment for microbial growth. They stay on the scalp and sometimes get into the eyes. They also include a wide range of ingredient types, from surfactants and silicones to dyes, keratin treatments and strong alkalis. Rinse-off products such as shampoos have different exposure from leave-on serums, and the safety assessor treats them differently. The category also has some of the most regulated ingredients in the annexes of Regulation (EC) No 1223/2009, such as hair dye substances.

Read also Hair Dye Testing: What the EU Requires Before You Sell

Step 1: Check the formula against the rules

Before any test, every ingredient and its level must be checked against the annexes: prohibited substances, restricted substances with maximum levels, and the positive lists of colourants, preservatives and UV filters. Hair care has a few points worth knowing:

• Hair dyes and colourants use substances that are strictly regulated and may carry specific warnings on the label.
• Smoothing and straightening products are restricted when they use ingredients that release formaldehyde or contain strong alkalis.
• Fragrance allergens must be declared when above set thresholds, and the list of declared allergens has been extended under Regulation (EU) 2023/1545 with phased-in dates.
• Synthetic polymer microparticles in rinse-off products are being restricted under the EU microplastics rules, with transition periods.

Our guide to the CPSR explains how the assessor uses this information; the CPSR is where every check is recorded.

Step 2: Stability and compatibility

A shampoo that looks perfect on the day it is filled can separate, thin out, change colour or lose fragrance after months in a warm bathroom. A stability and compatibility test stores samples under accelerated conditions, such as elevated temperature, and checks appearance, odour, colour, pH and viscosity over time. It also checks how the formula behaves in its real packaging: squeeze bottles, pumps, tubes or tubs. For hair oils, sprays and leave-in products, pump and valve performance matters as much as the formula. The results support the shelf life or the period after opening shown on the label.

Step 3: Microbiological quality of the finished product

Shampoos and conditioners are rich in water and often contain proteins, extracts and thickeners that feed microbes. A microbiological specifications test counts aerobic bacteria, yeasts and moulds and looks for specified harmful organisms in the finished product. SCCS guidance usually sets a stricter limit for products for children under three, for eye-area products and for mucous membranes than for other cosmetics, so a baby shampoo is judged against the stricter limit. The test is a snapshot of one batch, which is why it should be repeated for new batches and after formula changes.

Read also Aerosol Cosmetics Regulation: Dry Shampoo Testing and Shipping

Step 4: Preservation efficacy (challenge test)

Passing a microbiological test today does not mean the product will stay clean after consumers use it for months. The challenge test deliberately contaminates the product with reference microorganisms and measures how fast they die off over 28 days under a recognised standard such as ISO 11930. It is especially important for water-based shampoos, conditioners and masks. Low-water products such as solid shampoo bars or anhydrous oils may need a different assessment, and the assessor decides based on the formula and water activity.

Step 5: Skin and scalp tolerance

A formula can be safe by ingredient review and still cause reactions in a few people. Hair products often sit on the skin for minutes and may be used with warm water that increases penetration. A patch test on human volunteers supports claims such as “dermatologically tested” or “suitable for sensitive skin”. It is a tolerance study and does not replace the safety assessment. Animal testing of cosmetics is banned in the EU, so safety evidence relies on existing data, validated alternative methods and human studies.

Special cases in hair care

These are the situations where a generic shampoo plan is not enough. Talk to your assessor early, because a change of product type can change the whole test list and the labelling that goes with it.

• Hair dyes: follow the ingredient restrictions and labelling warnings, and make instructions for use unambiguous.
• Straightening treatments: check formaldehyde and alkali limits and the labelling that comes with them.
• Anti-dandruff products: the active ingredient usually has a permitted maximum level, and the claim must match the product’s function.
• Dry shampoos and sprays: aerosols need extra attention to propellants, inhalation exposure, pressure-safe packaging and raw-material purity.
• Baby and children’s shampoos: expect stricter microbiological limits and a careful look at mildness and eye irritation.
• Natural and herbal products: plant extracts support microbial growth and contain allergens, so they need good preservation and a safety review of each extract.

Read also Baby Care Product Testing: What Infant Cosmetics Need

Hair claims need evidence

“Reduces hair loss”, “repairs damage”, “grows hair faster”, “sulphate-free”, “scalp-friendly”: each of these has to be truthful and supported. Claims about hair loss or growth can slide into medical territory, and “repair” must be understood as an effect on the hair surface, not on the living cells. Match every claim to the evidence you have, and remove it if you do not have it. The EU rules on cosmetic claims require them to be legal, truthful, evidenced, honest, fair and to support informed choice.

A hair care testing checklist

1. Check each ingredient and its level against the current annexes.
2. Finalise the formula and the packaging together.
3. Run a stability and compatibility test in the final pack.
4. Run a microbiological specifications test on the finished product.
5. Run a challenge test for water-based formulas.
6. Run a patch test if you plan to claim skin or scalp tolerance.
7. Obtain the signed CPSR, complete the product information file and notify the product.
8. Re-test after any change of formula, supplier or pack.

Frequently asked questions

Does a shampoo need a challenge test?

If it contains water, almost always yes, because preservation must be shown to protect the product during use. Your safety assessor makes the final decision for each formula.

Do I need new tests for every fragrance or colour variant?

Often yes, or at least an assessment of each variant. A new fragrance or colour can change safety, stability and preservation, so ask your assessor which variants can share data.

Are hair products tested on animals?

No. Animal testing for cosmetics is banned in the EU. Safety is shown with existing data, validated alternative methods and human volunteer studies.

Key takeaways

• Hair products need a signed CPSR based on stability, microbiological and preservation data.
• Rinse-off products still need preservation, because they sit in wet bathrooms for months.
• Dyes, straighteners, dry shampoos and baby products carry extra rules.
• Every hair claim needs evidence, and every change needs a review.