Solid shampoo and conditioner bars are one of the fastest-growing categories in indie beauty plastic-free, travel-friendly and popular with eco-conscious shoppers. But a bar is still a cosmetic, and selling one in the UK or EU means it needs a CPSR like any other product. This guide explains what a safety assessment covers for solid hair bars and the points that most often catch makers out.
If you are new to safety assessments, start with our guide to what a CPSR is and the overall what you need to sell cosmetics legally. Here we focus on the specifics of solid bars.
Are shampoo and conditioner bars cosmetics?
Yes. A product intended to be applied to the hair and scalp to clean or condition it is a cosmetic under UK and EU law, whether it comes as a liquid in a bottle or a solid bar. The format does not change the classification. That means a shampoo bar or conditioner bar needs the full compliance set a CPSR, a Product Information File, a Responsible Person, notification and compliant labelling exactly like a bottled equivalent.
It is worth stressing this because the “natural”, “solid” or “plastic-free” positioning of many bars can give the impression they sit outside normal cosmetic rules. They do not. The eco-credentials are a marketing strength, not a regulatory exemption, and the safety assessment is just as necessary.
How shampoo bars are formulated
Most modern shampoo bars are built around synthetic or naturally derived surfactants cleansing agents such as sodium cocoyl isethionate (SCI), sodium coco-sulfate (SCS) and others pressed into a solid form, often with conditioning agents, oils and fragrance. This makes them quite different from a traditional cold-process soap bar, which is made by saponification. A surfactant-based shampoo bar is essentially a solid version of a liquid shampoo, not a soap.
This distinction matters for the assessment, because the safety considerations follow the ingredients. The surfactants, their concentrations, the pH of the bar in use, and any conditioning or active ingredients all feed into the evaluation. Knowing your exact formulation every surfactant and its percentage is therefore essential before a CPSR can be done.
The pH question
Hair and scalp tolerate a mildly acidic to near-neutral pH best, so the pH of a bar in use is an important safety and performance point. Shampoo bars are generally formulated to be reasonably balanced, while a true soap-based bar is alkaline and can leave hair feeling rough. Conditioner bars, which often rely on cationic conditioning agents, are typically formulated on the acidic side to help close the hair cuticle.
The safety assessment looks at pH because an extreme pH can irritate the scalp and eyes and damage hair. For makers, this means measuring and controlling the pH of your bars, and being able to provide that information for the assessment. A bar that performs beautifully but sits at an unsuitable pH is a problem the CPSR will flag.
Conditioner bars and cationic ingredients
Conditioner bars usually depend on cationic (positively charged) conditioning agents such as behentrimonium methosulfate (BTMS) and similar materials, which cling to the hair to smooth and detangle it. These ingredients are effective and widely used, but several conditioning and “quat”-type ingredients are restricted under the annexes, with maximum concentrations and conditions of use.
This is one area where a conditioner bar needs careful checking against the restricted-ingredient list see our guide to restricted cosmetic ingredients. Using a conditioning agent above its permitted level, or in a way its entry does not allow, makes the product non-compliant even though the ingredient itself is legal. The assessor confirms each conditioning ingredient is within its limits.
Surfactants, eye irritation and mildness
Surfactants clean by design, and some can be irritating to the eyes and skin at higher levels or in harsher types. Because shampoo inevitably runs near the eyes, eye-area tolerance is a genuine consideration, and the choice and level of surfactants influences how mild the product is. Blending surfactants and including mild conditioning agents are common ways makers improve tolerance.
The safety assessment considers the surfactant system's irritancy potential as part of judging whether the product is safe in normal and foreseeable use including getting some in the eyes. This is one reason the exact surfactant blend and its concentrations matter so much to the assessment, and why label warnings such as avoiding contact with the eyes are common on these products.
Do shampoo bars need a preservative?
This is one of the most misunderstood points. A solid bar contains little or no water, so in the bar itself there is generally little to support microbial growth which suggests no traditional preservative is needed. However, bars live in wet shower environments, sitting in pooled water between uses, and water repeatedly contacts the surface. This real-world wet use is why some makers and assessors take a cautious view on preservation.
The safe approach is to consider how the bar is actually used and stored, not just its dry composition. Where repeated wetting is likely, preservation or careful formulation and testing may be appropriate. Our guides to cosmetic preservatives and the challenge test explain the principles; the assessor decides what your specific bar needs based on its formula and use.
Stability and the bar staying solid
A bar has to stay solid, intact and effective over its shelf life not crumble, sweat, go soft, develop spots or smell off. Oils can oxidise and go rancid, surfactants can absorb moisture, and fragrance can fade. Stability testing helps confirm the bar holds up over time and in realistic conditions, which underpins the durability you put on the label.
Because bars are handled wet and left in humid bathrooms, their stability story includes how they cope with moisture and drying cycles. Our stability testing guide covers the general approach; for bars, paying attention to how the product behaves when repeatedly wetted and dried is particularly relevant.
Fragrance and allergens in hair bars
Many bars are scented, often with essential oils, and the same fragrance-allergen rules apply as to any cosmetic. Declarable fragrance allergens must be named in the ingredient list when present above the relevant threshold, and because a shampoo bar is a rinse-off product, the higher rinse-off threshold applies. Conditioner bars can sit somewhere between, depending on how they are used.
Getting the fragrance allergens right means knowing the allergen content of your fragrance or essential oils see our allergen labelling guide. The assessment and the label both depend on this data, so gathering it from your fragrance supplier is an early step.
Labelling a solid bar
Bars present a practical labelling challenge because there is often no bottle to print on. You still need the full mandatory information INCI ingredient list, Responsible Person details, net weight, durability or PAO, batch code, function and any warnings so a well-designed wrap, box or tag is usually the answer. The rules allow some information on attached or accompanying material where the bar itself cannot carry it.
Because “naked” plastic-free packaging is part of the appeal, makers sometimes try to minimise labelling, but the mandatory information cannot be dropped for aesthetic reasons. Our ingredient list and label warnings guides cover what must appear; the trick is fitting it elegantly into eco-friendly packaging.
Common shampoo bar mistakes
A few errors recur with solid hair bars. The first is confusing a soap bar with a shampoo bar selling a high-pH saponified bar as “shampoo” when its alkalinity is poorly suited to hair, leaving it rough and the scalp unhappy. The second is ignoring the wet-use preservation question, assuming “solid means no preservative needed” without thinking about the bar sitting in shower water between uses. The third is overloading conditioner bars with cationic agents beyond their restricted limits in pursuit of slip and softness.
A further common slip is minimal labelling letting the plastic-free, naked-product aesthetic crowd out the mandatory information, so a beautiful bar ships without a proper INCI list or RP details on its wrap or tag. None of these mistakes means a bar is inherently unsafe, but each is a compliance gap that a marketplace check or safety assessment will surface. The fix in every case is the same: treat the bar as the cosmetic it is, get the formula and pH right, think about real wet use, and label it fully then have it assessed.
Key safety points for hair bars at a glance
| Consideration | Why it matters |
|---|---|
| Surfactant system | Drives cleansing, mildness and eye/skin tolerance |
| pH in use | Affects scalp/eye comfort and hair condition |
| Cationic conditioners | Often restricted — must be within annex limits |
| Preservation | Solid but used wet — consider real-world water contact |
| Stability | Must stay solid and intact through wet/dry cycles |
| Fragrance allergens | Declare above the rinse-off threshold |
Shampoo & conditioner bar checklist
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Know your full surfactant and conditioner formulation and percentages.
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Measure and control the pH of the bar in use.
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Check cationic conditioning agents against restricted-ingredient limits.
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Consider preservation given wet, repeated use.
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Confirm stability through realistic wet/dry conditions.
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Declare fragrance allergens and fit full labelling onto eco packaging.
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Have it all assessed in a CPSR.
Selling shampoo or conditioner bars? Phoenix Safety Consultants assesses solid hair bars properly surfactants, pH, conditioning agents, preservation and labelling and provides your CPSR, PIF and notification for the UK and EU.
Get a Bar CPSR →Frequently asked questions
Do shampoo bars need a CPSR?
Yes. A shampoo or conditioner bar is a cosmetic, so it needs a CPSR, PIF, Responsible Person, notification and compliant labelling just like a bottled product. The solid format makes no difference.
Are shampoo bars the same as soap?
Usually no. Most shampoo bars are built from synthetic or naturally derived surfactants pressed into a solid, not made by saponification like a soap bar. This affects their pH and how they are assessed.
Do solid bars need a preservative?
It depends. The dry bar has little water to support microbes, but bars are used and stored wet, so repeated water contact may justify preservation or careful formulation and testing. The assessor decides based on your formula and use.
Why does the pH of a bar matter?
An unsuitable pH can irritate the scalp and eyes and damage hair. Shampoo bars are generally formulated balanced, and conditioner bars usually slightly acidic; the CPSR checks the pH is appropriate.
Are conditioner bar ingredients restricted?
Often the cationic conditioning agents used in conditioner bars are restricted under the annexes, with maximum levels and conditions. The assessment confirms each is used within its limits.
How do I label a plastic-free bar?
Use a wrap, box or tag to carry the full mandatory information INCI list, RP details, net weight, durability or PAO, batch code, function and warnings. The information can't be dropped for aesthetics, but it can sit on accompanying packaging.
Do I need to declare fragrance allergens in a bar?
Yes, when present above the relevant threshold. A shampoo bar is rinse-off, so the higher rinse-off threshold applies; you need your fragrance's allergen data to declare correctly.
References: Regulation (EC) No 1223/2009 (EUR-Lex); Annex III restricted substances; ISO 11930; UK Cosmetics Regulation as retained. General information only, not legal advice.
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