108 FORMULATING FOR MILDNESS
can be amphoacetates, cocodiethanol amide, coco mono-ethanol amides etc. Some of the benefit components such as glycerin, vitamins, antioxidants, and antibacterial agents can be added at appropriate levels to get formulation of required benefits. In shampoos one can have additional ingredients such as antidandruff components, conditioning agents and anti-lice etc. The conditioning components can be silicon based or cationic polymers. The pH of these formulations can be adjusted to 5.5-7.0 based on the requirements. These formulations can be very mild and provide high level of foaming properties. With minor changes in the formulation these products can be used as liquid hand wash, shower gel, body wash and shampoos. The formulations for most of the liquid cleansers look alike but their performance can be changed by adding the benefit components to get different products such as liquid hand wash, shampoo, body wash, shower gel, etc.
Methods of clinical studies for estimation of mildness There are several methods which are used for the determination of the mildness and moisturisation properties of different products. A brief description of some of these methods is given below:
Zein solubility test Zein Solubility test provides us the quantitative figure to determine the potential of skin irritation. The skin irritation potential is directly proportional to the solubility of zein in the surfactant solution. The surfactant solution denatured the zein protein.7
The zein is basically a type of protein found in maize which is slightly
Table 7: Transparent soap formulation. Ingredients
%
Anhydrous Soap Polyols Water
Perfume Non soapy actives
50 – 60 15 – 25 18 – 20 0.5 – 1.0
0.00 – 5.00
soluble in water. The zein powder at about 4-6% wt is mixed in the surfactant solution for 24 hours. The solution is then filtered and the clear solution is obtained. The concentration of zein in the solution is finally determined through UV absorbance.
Flex wash test
Flex wash test is a very effective method to determine the skin irritation potential. The major advantage of flex test is that it does not depend upon weather conditions. In this test male and female volunteers of different age groups are selected. One has to make sure that the subject taken for a test does not have any dermatological disease history. Normally two products are assessed with the single subject, one product on the right arm and other on the left arm. Flex area of an arm is first cleaned then washed with the product gently for 60 seconds. After that the arm is rinsed with the tap water until all lather is removed and then is dried by pat drying using a soft towel. The area on the arm is assessed after every 1.5-2 hours of washing. This procedure is carried out three times a day and continued for 5 days or until moderate erythema is observed. The flex area is evaluated by the assessor; the assessors give their rating based on the appearance of erythema on the skin.8
Table 8: Soap based liquid formulation. Ingredients
Laurate/ Oleate mixture Polymers Perfumes
Other benefit components Water
Patch test
This method was developed for the quick evaluation of skin irritation potential.9
In this
test known concentration of patch of the surfactant solution is applied to the forearm area of skin for certain period of time normally 6-12 hours. After that patch is removed from skin and patch site is cleaned with a soft towel. The patch site is then evaluated by the trained examiner and rating is given based on redness and dryness of skin on 0-3 or 0-4 scale. This procedure is continued for another 6-7 days till the erythema (redness) symptoms appear. If the redness of skin appears at the first stage then future evaluation is discontinued and the product classified as the irritant.10
Forearm Controlled Application Test (FCAT)
40 28
Commonly known test for determining skin harshness potential, erythema and trans epidermal water loss (TEWL) from the skin.11 This test is also known as FCAT. In the FCAT test, male and female participants of different age group are selected, the total time for FCAT test is 7 days in which one part of the test is conditioning and another part is of application. In the conditioning phase participants are requested not to use moisturisers on the test site area of a forearm and clean it with a special single surfactant formulated product for 4-5 days. After that in the application phase, the forearm sites are washed with the product 3 times daily after every 2 hours. During application phase, the forearm sites are examined and the rating of erythema is given based on the visual observation of the severity of the redness. Besides visual rating Skicon 100 or 200 used to get the variation in conductance of the skin which in turn helps in understanding the hydration behaviour by the application of the product.10
the trans epidermal water loss by the product application.12
1:1 Laurate Figure 4: Mixture of laurate and oleate. PERSONAL CARE EUROPE Ratio Oleate
Frosch-Kligman soap chamber test This test method was developed in 1979 to determine skin irritation potential by applying a surfactant product on the skin. The total time of test is almost 5 days.13
On
the first day, the product is applied to the forearm area of skin for 24 hours. For the rest of the four days the same product is
April 2019 %
15.0 – 20.0 0.3 – 1.0 0.5 – 1.0 1.0 – 2.0 80 – 85
DermaLab TEWL is used to check
Temperature °C
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