Personalised skin care – technological and legal requirements

Provided the institute staff are well trained, they have experience in recognising skin conditions and also many dermal (medical) indications. Devices help to record skin moisture, skin lipids, transepidermal water loss, skin elasticity, pigmentation and surface structure (camera), to name just the most important parameters. This allows the current condition of the skin to be determined, a target defined and compared with the result after treatment. If skin hydration is low, for example, you will want to increase it.
For this purpose, the institute's repertoire includes products that are differently suited to the skin in question. A choice has to be made, e.g. between a W/O and an O/W emulsion. If the moisture deficit is high, the W/O variant will be chosen and the treatment may be combined with a moisturising fleece mask or a hardening, ultimately occlusive mask. Combining individual products will therefore bring you closer to your goal. 

Sera versus multifunctional products

When using masks, several products are often mixed and applied in different ratios in order to not only increase skin moisture, but also to achieve skin smoothing and other effects. In these cases, individually customised multifunctional products are often not available. Several products are used all the more if they are available in the form of sera, which essentially only contain one active ingredient in a higher concentration. What initially appears to be cumbersome and a shortcoming has a decisive advantage: components of multifunctional products that are not suitable for the skin in question can be excluded – substances or extracts, for example, to which dermal or mental sensitivities or reservations exist. 

Physiological components

In order to generally exclude sensitivities as far as possible, it is also advisable to use only physiologically compatible compositions for sera, but preferably also for multifunctional products, which can be integrated into the body's metabolism without interference. This significantly increases the safety of treatment with mixtures and products of different compositions. 
Some sera have a penetration-enhancing effect on active ingredients and other sera used together. This situation is encountered, for example, in combination with liposomes containing phosphatidylcholine. This increases the bioavailability and effectiveness of active ingredients. One example is azelaic acid, which experience has shown to have a comparable effect in liposomal dispersions of up to 1% on "blemished skin"¹ as when it is used in two-digit concentrations in O/W emulsions for the medical treatment of acne. A further advantage is that the initial irritation associated with high concentrations is completely eliminated.

Preservatives

At this point, the topic of preservatives should also be mentioned, as they all have allergenic potential – the main reason, incidentally, that they are listed in a separate annex to the Cosmetics Regulation². In other words, (non-physiological) preservatives should be completely excluded when experimenting with mixtures. This is easily possible according to the current state of the art. Even in the past, sera were used in ampoules that were filled sterile or sterilised at high temperatures. The skin flora, alias the microbiome, will welcome this.

Shelf life

As product combinations (mixtures) are usually freshly prepared, used ad hoc and not stored, their physical, chemical and microbial shelf life does not play a role for the time being. Keep in mind: 

• Physical instability manifests itself in the separation of water and oil phases, for example. The loss of a substance from a dispersion would be noticeable as turbidity or a sediment.  
• Chemical instability includes autoxidation, i.e. sensitivity to atmospheric oxygen and radiation. 
• However, a chemical reaction can also occur between two substances, for example when a strong antioxidant meets an easily reducible compound. Free vitamin C (ascorbic acid)³ and coenzyme Q₁₀ are such a combination. In this particular case, the antioxidant capacity of coenzyme Q₁₀ is activated and the ascorbic acid is inactivated.
• Microbiologically, undesirable bacterial or fungal growth can occur if cream or serum bases are not coordinated with each other, i.e. the mixture – i.e. dilution – falls below the minimum inhibitory concentration (MIC) for certain germs. 

However, if there is a certain amount of stockpiling because a mixture is constantly used in the institute's practice or is particularly effective, then these criteria must be taken into account. In other words, it is advisable to avoid products or sera with different compositions and to use modular systems specially designed for this purpose, in which all components are harmonised in terms of physics, chemistry and microbiology.   

Home care – DIY brand

In addition to the aforementioned mask treatments, wraps, massages, etc., which are mainly carried out at the institute, enthusiasm for personalised anti-ageing creams is growing rapidly. Especially when they show their full effect as soon as you leave the practice, the desire for adequate care at home arises.
What sounds plausible in practice is only legally possible (Cosmetics Regulation) if the cosmetics institute mutates into a manufacturing company for the mixtures. But the associated requirements are usually beyond the financial scope. However, it is possible for the beautician to resell the individual components of the creams as they are purchased from the manufacturer. By providing customers with the mixing ratios (recipe) and, if necessary, the containers, the same cream can be reproduced and used at home. The kitchen utensils make it possible.

Personal care to go

Modular systems enable the beautician to provide a service. And it works like this:

• As with individual dermatological formulations in pharmacies, there are cream bases (base creams) with different compositions into which active ingredient concentrates can be mixed. They differ, for example, in their lipid content, their consistency or their technical structure. While pharmacies very often use paraffinic W/O base creams, bases with an O/W or lamellar structure are preferred in skin care. Paraffin bases create occlusive conditions on the skin, the skin swells and allows drugs to penetrate more easily transdermally. These bases are now rarely used in skin care, as skin regeneration suffers as a result. This principle used to be popular with night creams, as the swelling of the skin overnight led to a temporary reduction in wrinkles.  
• The corresponding sera (active ingredient concentrates) are either still offered in ampoules or, more appropriately, in containers from which discrete quantities can be removed using a pipette or bottle graduation. As the sera often have a water-like consistency, they can also be used as lotions, which can also be customised.
• While pharmacies use electric mixing tools⁴ such as the Unguator^® or Topitec^®5, the institute uses a simple spatula, among other things, to add and mix the sera in a suitable container. Prefabricated dispenser bases, in which the base cream may already be present and a free dispenser volume allows certain amounts of sera to be added, are practical. At the end, the dispenser is closed with a head section from which the mixed cream is later removed.

As already mentioned, institutes are not allowed to offer products mixed in this way as finished products, even if the formulas become bestsellers. This naturally includes warehousing and advertising in shop windows and on the Internet. It is only possible to pass on the products as "one-offs" – personalisation in the truest sense of the word – as part of a personal and paid service that includes mixing on behalf of the customer. 

Automated personalisation

The skin analysis and its transformation into a customised formula can also be created automatically. This is nothing new in principle. Skin analysers with probes for the various skin parameters, whose measurement results are linked to a manufacturer's finished products via software, have been around for a long time. They are used in institutes, dermatological practices and pharmacies to filter out the optimum product for users from the wide range on offer. Without skin analysis, the correlation can also be made using electronic questionnaires.
A similar principle has been used by setting up vending machines in shopping centres that determine the skin condition based on measurements of, for example, skin moisture and skin lipids and/or with question & answer and translate this into a preparation mixed on the spot that can be taken directly from the machine. Here too, base creams and a manageable number of sera are used. However, what initially appears to be very practical has not proven to be optimal, as these machines lack the non-digitised experience of an institute on the one hand and on the other hand both the measurement parameters and the number of formulation components are limited – not to mention the fact that the popularity of individual active ingredients in the industry is subject to strong fluctuations. This is why the machines have not become established.
Legally, the vending machines operate in a similar way to an independent, registered factory whose formulations are registered in the European Cosmetic Products Notification Portal (CPNP)⁶ in accordance with EC Regulation 1223/2009.

Skin condition and indication

The identification of the individual skin constitution goes beyond the skin condition and also takes into account indications as far as possible, i.e. the presence of acne, rosacea, psoriasis, neurodermatitis, for example, i.e. keratinisation, barrier, connective tissue, vascular and pigmentation disorders. In some cases, the indications are recorded in the institutes using anamnesis-like documentation and integrated into the considerations for treatments and care products. 
The ideal, but still rare, constellation is the cooperation between a beauty institute and a dermatological practice. This collaboration enables coordinated, holistic personalisation:

• The dermatological practice makes the medical diagnosis and provides treatment with topical or sometimes oral medication for as long as necessary.
• Skin care is adapted to the medical therapy. If necessary, it also compensates for the side effects of the therapy. This is referred to as adjuvant care. Clinical studies show that this can make the therapy more efficient and shorten it.⁷
• Once medical therapy has been completed, skin care should be adjusted in such a way that optimum prevention is achieved and a relapse of the therapy is avoided.
• Within corneotherapy^8,9 and elsewhere, it makes sense to use the same base creams for all stages of therapy and prevention. This causes fewer problems in terms of compliance as the users are already familiar with the cream. 
• If the composition of the base cream complies with the requirements of the European Pharmacopoeia¹⁰ or the corresponding Drug Master Files (DMF)¹¹, then it is easier for the pharmacy to prepare the individual dermatological formulation.¹² Cosmetic active ingredients can also be processed together with the medicinal products if they are documented accordingly. 
• Some medicinal substances can continue to be used in skin care products for prevention after therapy if the obligatory safety assessment¹³ allows it in terms of concentration. Examples include azelaic acid, tranexamic acid, D-panthenol, clotrimazole and piroctone olamine. However, appropriate advertising with mention of the indication is only possible to a limited extent. You will then find formulations such as "For the supportive prevention of..."

 
Personalised skin care – technological and legal requirements

Part II: Holistic personalisation – Software

Software solutions are crucial for the personalisation of skin care, especially in the adjuvant treatment of specific skin indications. However, the exact quantification of the effects of cosmetic and pharmaceutical ingredients remains a challenge. In part II of this article, we look at why this is the case and what solutions are available.

Software solutions are of great importance for holistic personalisation – especially with the inclusion of adjuvant care for indications such as finished cosmetic products and modular systems. However, there is a lack of exact digital data on many components with regard to their effect on the skin. 

• Depending on their concentration, the effects of cosmetic active ingredients cannot be quantified exactly.
• There is no reliable data on the behaviour of cosmetic and pharmaceutical active ingredients with regard to their penetration, permeation and depot effect in the skin barrier when they are present in mixtures of different concentrations and base creams.
• Dose-effect relationships for mixtures are largely lacking and can only be determined in individual cases due to the infinite number of possible combinations. 

It is therefore partly reliant on judgements, but these are refined step by step as in a learning AI. Ultimately, measured values from the skin analysis are processed or skin conditions such as "dry", "low-fat" and indications such as "acne", "rosacea" are queried and correlated with the corresponding properties and concentrations of formulation components. It is also important to recognise counterproductive effects such as high lipid concentrations in the case of acne. Ultimately, mixtures can be evaluated for their individual suitability and optimised. 

Compatibility of the components

When manufacturing personalised products, the major challenge is still to ensure that the components are technically compatible with each other. Auxiliary substances should be excluded as far as possible in order to avoid unnecessarily stressing the skin. 
In addition, skin protection and the desired effect must be in a reasonable relationship to each other if only one product is to be used. Lamellar bases are particularly suitable for this. Base creams with hydrogenated phosphatidylcholine in particular can be adjusted seamlessly from pure skin protection to pure active ingredient with active ingredient-laden liposomes based on native phosphatidylcholine.
Background: Due to their structure, the base creams behave like the skin barrier and integrate the liposomes in the same way.
One disadvantage of lamellar systems is their sensitivity to admixtures containing strong synthetic emulsifiers, which in turn are detrimental to the skin due to their wash-out effect during subsequent skin cleansing. Incidentally, this effect also speaks against corresponding formulations that are still commonplace in pharmacy formulations today. In this respect, cosmetic formulations today are much more technologically advanced than pharmaceutical NRF formulations (NRF = New Formulation Formulary¹⁴).
Speaking of skin protection: If you want to achieve optimum effectiveness and skin protection, the treatment can also be divided into two steps. Firstly, the skin is treated with liposomal or nanodisperse active ingredients that penetrate well into the skin. In a second step, the desired skin protection is achieved by applying pure lamellar base cream.    

And what doesn't work...

All personalised skin care procedures are based on the assumption that the base creams or base lotions as well as the sera and active ingredient concentrates are components, all of which are registered as commercial products in the Cosmetic Products Notification Portal (CPNP) in accordance with the Cosmetics Regulation. Chemicals, including sun protection filters and even banal household substances such as sea salt and granulated sugar, are not permitted. However, it is not necessarily checked if a salt or sugar peel is carried out at the institute. But it is important to realise that the institute bears full responsibility in the event of "undesirable side effects", which cannot be passed on to the salt or sugar supplier. 
The situation is different for pharmaceutical prescription medicines. Pharmacists can of course add individual substances such as urea. Sometimes even high concentrations are used in this specific case so that the costs can be reimbursed by the health insurance companies.
If purely cosmetic preparations are prescribed in pharmacies, they are no longer subject to the Pharmacy Operating Regulations, but to the Cosmetics Regulation. Pharmacies are then subject to the same restrictions as cosmetics institutes. Many pharmacists only realise this when the Veterinary and Food Inspection Office arrives at their door and wants to see the production permit.

References and remarks

1. The European Cosmetics Regulation does not permit the targeted cosmetic treatment of medical indications.
2. Annex V of the European Cosmetics Regulation; https://www.gesetze-im-internet.de/kosmetikv_2014/BJNR105410014.html
3. Note: Free ascorbic acid is often replaced in cosmetics by its phosphoric acid ester, Ascorbyl Phosphate (INCI).
4. Lautenschläger H, Eine gute Basis – Pharmazeutische und kosmetische Basiscremes, medical Beauty Forum 2016 (5), 12-17
5. Blue text: Not included in the original publication
6. https://webgate.ec.europa.eu/cpnp
7. Suvorova K, Corneotherapy of skin diseases accompanied by epidermis disorder (in Russian), Les Nouvelles Esthétiques (Russian version) 2004;4:28
8. Lübbe J, Evidence-Based Corneotherapy, Dermatology 2000; 200:285-286
9. Tabata N, O'Goshi K, Zhen YX, Kligman AM, Tagami H, Biophysical assessment of persistent effects of moisturizers after their daily Applications: Evaluation of Corneotherapy, Dermatology 2000;200:308-313
10. Pharmacopoea Europaea [Ph. Eur.]; https://www.bfarm.de/DE/Arzneimittel/Zulassung/Zulassungsrelevante-Themen/Arzneibuch/_node.html
11. https://de.wikipedia.org/wiki/Drug_Master_File
12. Pharmacy Operating Regulations (ApBetrO); https://www.gesetze-im-internet.de/apobetro_1987/BJNR005470987.html
13. Guidelines on Annex I to Regulation (EC) No 1223/2009 of the European Parliament and of the Council on cosmetic products; https://eur-lex.europa.eu/legal-content/DE/TXT/PDF/?uri=CELEX:32013D0674&from=EN
14. https://dacnrf.pharmazeutische-zeitung.de

Dr Hans Lautenschläger

published in
Medical
2025 (2), 15-19 und
2025 (3), 20-21