Composition of Clearing Cream

Composition of Clearing Cream
1. Basic Concepts of Clearing Cream
1. Definition and Main Uses
Clearing cream is a semi-solid skincare preparation designed with the concept of "first remove and then replenish". Its core task is to simultaneously dissolve makeup, clear sebum, and soothe barriers within a single application. Its English name is often translated as "cleansing ball". Its texture is in the form of a paste at room temperature, which quickly melts into an oil upon contact with the skin. When it comes into contact with water, it emulsifies into microbubbles and can eventually be completely taken away by warm water. Compared with makeup remover, the formula oil content of Emptying Cream is higher, and it has stronger swelling power for waterproof sunscreen and durable foundation make-up; Compared to makeup remover oil, the cream form is easy to carry during travel and less prone to dripping. The mainstream applications cover four major scenarios: makeup removal, deep cleaning, blackhead softening, and surface keratin conditioning. Some formulas additionally add ceramides or squalane to reduce the water loss rate of the stratum corneum by about 12% to 18% after cleaning, thus meeting the dual needs of "removal" and "nourishment".
2. Common product types
Based on the differences in oil-based types and emulsion systems, there are three major sub types visible in the market. The first type is pure alkyl type, mainly composed of microcrystalline wax and hydrogenated polyisobutene, with controllable cost and high stability, suitable for stage makeup people with high makeup intensity; The second type is plant wax ester type, which uses a combination of sunflower seed wax and jojoba ester. Its melting point is close to the temperature of human skin, and it has strong extensibility. It is often used by sensitive skin brands; The third type is the silicone wax composite type, which adds cyclopentasiloxane to the oil phase to provide a "silky dry glove like" skin feel, but the proportion of silicone oil needs to be controlled below 20%, otherwise there may be residual oil film during subsequent emulsification. All three types of products are formed through the "high temperature pouring low temperature reheating" process, and the filling temperature is usually controlled between 65 ℃ and 70 ℃ to ensure that the paste does not sweat or sink in a 45 ℃ transportation environment.

2、 Main ingredient classification
1. Cleaning agent ingredients
Cleaning agents undertake the three-stage task of "swelling wrapping detachment" in the formula, usually accounting for 30% to 50% of the total amount. The mainstream choices include three technical routes: non-polar hydrocarbons, polar esters, and silicone oils. The non-polar route is mainly composed of mineral fat and C15-19 alkane, which have a fast swelling speed for cosmetic pigments, but limited cleaning power for polar dirt; The polar route introduces PEG-20 glycerol triisostearate ester, which has an HLB value of about 18 and can quickly form a water in oil microemulsion with water, reducing the need for secondary cleaning; The silicone oil route utilizes the low surface tension characteristics of cyclic siloxanes to dissolve corner plugs deep into pore openings, but requires the use of 0.5% to 1% polyether modified silicone oil as an emulsifying bridge, otherwise a "silicone film sensation" may occur after rinsing. The three types of raw materials are often combined using the concept of "polarity gradient compounding" to cover the range of polarity differences from 0 to 14, thereby achieving broad-spectrum dissolution of various types of dirt.
2. Moisturizing agent ingredients: Moisturizing agents are not simply "hydrating" in the cleansing cream, but reduce the loss of transdermal moisture during the cleaning process through a three-level mechanism of "sealing, moisture absorption, and repair". The sealing layer often uses squalane and shea butter, both of which have an evaporation pressure below 0.01 mmHg at 25 ℃ and can form an invisible oil film that lasts for more than 4 hours; The moisture absorbing layer is often mixed with 2% to 5% glycerol or dipropylene glycol, which forms a hydrogen bond network with hydroxyl groups and water molecules, causing the moisture content of the stratum corneum to increase by about 8% within 15 minutes after cleaning; The repair layer adds 0.3% to 1% ceramide NP to supplement intercellular lipids and reduce the extraction of desmin by surfactants. To balance the hardness of the paste, the refractive index of the moisturizing oil needs to maintain a difference of less than 0.02 with the main wax base, otherwise high temperature storage may cause "oil leakage" or "frosting".
3. Auxiliary additives
(1) The water activity (aw) of the preservative clearing paste is usually less than 0.6, which can theoretically be called "non preservative", but the production filling and repeated opening by consumers may introduce microbial risks.
. The mainstream strategy adopts a combination of low-dose polyols and acids, compounded with 1,2-hexanediol, octanohydroxamic acid, and ethylhexylglycerin, with a total dosage controlled at around 1.2%. This can reduce Staphylococcus aureus and Pseudomonas aeruginosa in the challenge experiment to below 10 CFU/g within 48 hours. The pH range of this system is 3.5 to 7.0, which naturally matches the neutral pH of the paste itself and avoids the thermal stimulation that may be caused by traditional phenoxyethanol.
(2) Spices and fragrances mainly serve the function of "emotional skincare" in clearing cream, but they must comply with the limitations of IFRA standards on photosensitivity and sensitization. The commonly used method is a three-stage structure of "head fragrance body fragrance base fragrance". The head fragrance is mostly citrus fruits such as limonene, the body fragrance is mainly composed of rose alcohol or lily of the valley aldehyde, and the base fragrance is extended with a small amount of patchouli alcohol. To reduce the sensitization rate, the total spice concentration in the formula is usually less than 0.3%, and a benzene free solvent (such as isopropyl myristate) is used for dilution to reduce the potential allergen content to less than 100 ppm. For products claiming to be "odorless", the inherent odor of the raw materials is reduced to below the odor recognition threshold through vacuum deodorization technology, rather than simply not adding fragrance.
3、 Detailed analysis of the functions of ingredients
1. Mechanism of action of cleaning agents
The core physicochemical process of cleaning agents can be simplified into three steps: "similar phase solubility interface substitution micelle solubilization". Firstly, non-polar hydrocarbons combine with makeup pigments and sebum squalene to form van der Waals forces, causing dirt particles to expand to 1.5 times their original size; Subsequently, polar esters reduce the interfacial tension between oil and water to about 5 mN/m due to the presence of hydrophilic groups, replacing the contact point between dirt and the stratum corneum; Finally, during the water flushing stage, PEG emulsifiers form multiple layers of micelles, encapsulating dissolved dirt into a hydrophobic core. The critical micelle concentration (CMC) is approximately 0.02 g/L, below which it can be carried away by flowing water. Experiments have shown that when the total amount of cleaning agents is ≥ 35% and the polarity/non-polar ratio is maintained at 3:7, the residual amount of zinc oxide sunscreen can be reduced to below 2% of the initial amount.
2. The efficacy principle of moisturizers: Moisturizing agents maintain barrier stability while cleaning through a three-axis linkage of "sealing moisture absorption repair". At 30 ℃, the enclosed oil forms a continuous film with a single molecular layer thickness of about 2 nm. Fourier transform infrared spectroscopy confirms that its CH ₂ symmetric stretching vibration peak is located at 2852 cm ⁻¹, overlapping with the lipid peak of the stratum corneum, indicating high compatibility; Moisture absorbing polyols can increase the conductivity of the stratum corneum by about 25% in an environment with a relative humidity of 50%, equivalent to an increase of 3 μ g/cm ² in moisture; Neuroamide NP supplements the lost lipid layer due to surfactant elution through the "insertion filling bridging" mechanism, shortening the barrier recovery time to 6 hours. The synergy of the three can reduce the peak TEWL (transcutaneous water loss) after cleaning to only 8 g/h/m ², much lower than the 20 g/h/m ² achieved by pure water cleaning.
3. The functional significance of additives Although preservatives and fragrances are "non functional" ingredients, they directly affect the product lifecycle and user experience. Preservatives increase intracellular ATP leakage rate by more than 10 times by disrupting microbial cell membrane potential, thereby inhibiting secondary pollution; Spices increase the proportion of alpha brain waves by about 12% within 30 seconds through the olfactory limbic system pathway, indirectly reducing cortisol levels and realizing the concept of "emotional skincare". In addition, trace antioxidants such as BHT (at a dosage of 0.01%) can inhibit the oxidation and rancidity of the paste, keeping the peroxide value below 5 mmol/kg in the accelerated test at 40 ℃ and extending the shelf life to more than 30 months.
4、 Safety and Precautions
1. Identification of Potential Allergens
Common allergens in the clearing cream include the spice limonene, preservative octanoyl hydroxamic acid, and associated proteins in plant wax.
. Limonene can generate limonene peroxide after oxidation, and its sensitization potential is about 20 times higher than that of the parent compound; Octahydroxamic acid decomposes into hydroxylamine at pH>6.5 and undergoes Schiff base reaction with keratin, with a probability of inducing contact dermatitis of about 0.05%; If plant wax is not subjected to high-temperature deproteinization treatment, residual protein fragments with a molecular weight of 10-50 kD can activate innate immunity through the TLR2 pathway. It is recommended that people with sensitive skin apply 0.2g behind the ear before the first use, and use it on the entire face after 48 hours without redness. At the same time, avoid known spice mixtures such as "HICC" or "formaldehyde".
2. Taboos and Risk Avoidance
For severe rosacea (papule pustular type) or acute eczema exudation, the use of clearing cream should be temporarily suspended, as the emulsification and rinsing process requires friction for more than 30 seconds, which may worsen capillary dilation; For the skin that has just undergone exfoliative dot matrix laser, due to the opening of the barrier, it is recommended to delay use until the 5th day after surgery and choose a formula without fragrance or silicone oil. If there is a phenomenon of "blurred vision", it is mostly due to silicone oil or wax entering the conjunctiva. It should be immediately rinsed with a large amount of physiological saline and checked for corneal epithelial integrity by seeking medical attention. In addition, pregnant women can use it normally, but it is necessary to avoid formulas containing salicylic acid derivatives, as high-dose salicylic acid may have potential effects on the fetus after transdermal absorption.

3. Correct storage method
Clearing the paste is sensitive to temperature fluctuations, and its wax base will form coarse spherulites during repeated melting crystallization processes, leading to the "sanding" of the paste. It is recommended to store in a cool environment with a temperature range of 15 ℃ to 25 ℃ and a relative humidity below 60%, avoiding direct heating in the bathroom. If there are "sweating" oil droplets on the surface of the paste, the product can be refrigerated at 4 ℃ for 2 hours and then warmed back to room temperature to form a uniform crystal network again. Try to use it up within 6 months after opening the lid to reduce the risk of oxidation and rancidity; If the odor changes from light to acidic, or if the peroxide value test strip shows>10 mmol/kg, it should be stopped immediately.
5、 Practical application guidance
1. Daily operation steps
The standard process is divided into four steps: "dry hands and face - emulsify - rinse - secondary inspection". The first step is to take about 1.5 g of cream (about the size of a cherry) in the palm of your hand, rub it with both hands for 3 seconds to make it initially melt, then evenly apply it to the face, massage with fingertips in a "heart-shaped" path for 30 seconds, focusing on strengthening the nose, hairline, and jawline; The second step is to take a small amount of warm water and continue massaging for 20 seconds. The paste changes from oil to milk, and the viscosity drops to about 2000 cP. At this point, the makeup has been completely wrapped; The third step is to rinse with flowing water at 32 ℃ to 34 ℃ for 40 seconds to avoid excessive degreasing of the barrier caused by high temperature; The fourth step is to gently press and absorb water with a pure cotton towel. If there is no makeup residue on the towel, it is considered clean. Otherwise, it can be emulsified again. The entire process consumes about 1.2 L of water, saving about 30% compared to traditional makeup remover.
2. It is recommended to use moisturizing spray containing 0.5% to 1% panthenol immediately after emptying the cream with other skin care products. Its panthenol molecular weight is only 205 Da, which can rapidly penetrate and cooperate with the clearing cream to remove the residual ceramide, improving the barrier repair efficiency by about 15%; Then use alcohol free light lotion, with the oil content controlled below 10%, to avoid overlapping with the residual oil film of the cream and causing stuffy acne. If it is necessary to add retinoic acid anti-aging products, it should be applied at an interval of more than 10 minutes after the oil phase on the skin surface has completely evaporated to reduce irritation. Daytime care must include broad-spectrum sun protection, as the thickness of the stratum corneum temporarily decreases by about 0.3 μ m after cleaning, and the UV transmittance can be increased by 8%. If sun protection is ignored, the risk of blackening is higher than that of uncleaned state.