Evaluation of Shampoo

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Chapter: Textbook of Cosmetic Formulation : Shampoos

According to the regulatory authorities each and every batch of shampoos must be evaluated prior to marketing. Evaluation is a measure of activity and safety. It also notifies the toxicity, if nowadays most of the shampoos are prepared, from synthetic detergents, hence evaluation becomes an essential factor.


EVALUATION OF SHAMPOO

 

According to the regulatory authorities each and every batch of shampoos must be evaluated prior to marketing. Evaluation is a measure of activity and safety. It also notifies the toxicity, if nowadays most of the shampoos are prepared, from synthetic detergents, hence evaluation becomes an essential factor. However, there is also a need to evaluate herbal shampoo, since it may contain natural ingredient which are liable to contamination.

 

 

Shampoos are evaluated for the following aspects.

 

(I)          Evaluation of Safety

 

(II)          Evaluation of Antimicrobial Property

 

 

(I)           Evaluation Of Safety:

 

Safety is an important aspect which must first and foremost parameter of evaluation. As stated earlier the shampoos are made from synthetic detergents, which are liable to irritate skin, scalp and eye. Hence, it becomes essential to evaluate the safety of a shampoo. Over all, the shampoo must be non-toxic and non-irritative. The safety is usually evaluated it, terms of toxicity i.e., if the preparation is found to be non toxic then it is regarded as safe and vice-versa. However, the toxicity is determined by using “Draize test” which suggests two separate methods for testing skin and eye toxicity respectively. The methods are as follows:

 

 

(a)          Skin Toxicity Test: The steps involved in this test are as follows:

 

A set of six albino rabbits are selected. They should weigh about 2 kgs.

 

On the skin of each rabbit, a round patch is made by removing hair.

 

Dilute preparation (8-10%) of shampoo is usually applied onto the patches of a rabbits.

 

The shampoo is allowed to react for a period of 3-4 hours. After that it is removed completely from the skin.

 

After efficient washing, the skin is examined for any adverse reactions such as erythema, edema etc.

 

Based on the results obtained the shampoo is considered as either safe or toxic.

 

Usually, there might be chances of adverse reactions because the shampoo was kept in contact for 4 hours. But usual practice of shampooing in human being is for 10-15 minutes. Alternatively, the skin test is also performed on human being.

 

 

(b)          Eye Toxicity Test: The steps involved in this test are as follows:

 

A set of six adult albino rabbits are selected. They must weigh about 2 kgs.

 

One eye of each rabbit is considered as test eye and another as control eye.

 

To each of the six test eyes of six rabbits, the product (shampoo) is applied.

 

Washing is done after 20 seconds pith 200 ml of tap water.

 

The eyes are rewashed after 5 minutes and then after 24 hours.

 

The control eye are also washed on first day and then after 24 hours.

 

The test eyes are observed at 1, 24, 48 and 72 hours respectively. They are also examined on 7th and 14th day.

 

The product is said to be toxic, if there is a development of iris and corneal lesions which remains for more than 7 days.

 

 

(II)           Evaluation Of Antimicrobial Activity:

 

Shampoos are liquid or viscous preparations, they are liable to microbial growth. Hence, preservative is usually added to prevent midi growth .The added preservative should have following properties.

 

 

·                               It should be non toxic.

 

·                               It should be compatible with other ingredients.

 

·                               It should be effective at low concentration,

 

·                               It should be effective against wide variety of microorganism.

 

 

However, all the above points are considered prior to the selection of preservative. Evaluation of preservative usually involves the study of antimicrobial activity is generally done by using a method called as "Challenge Study". According to this study, the product is said to be preserved when it does not support microbial growth even after repeated attacks of various micro-organisms.

 

 

Procedure (Challenge Study):

 

Initially an appropriate strain of microorganism is selected and is considered as test organism. Usually the species of Pseudomonas are selected i.e., P aeruginosa, P. Putida etc.

 

A culture of any one of the above test organisms is prepared.

 

The product (shampoo) is then inoculated repeatedly in the culture medium and the studies are carried out for a period of 10 to 12 weeks.

 

 

The inoculums usually contain 5 lakhs to1 crore micro organisms/ gm of product. Along with the test, control samples are also prepared and reserved for reference. Usually two types of control samples are prepared i.e., one sample with preservative and another without preservative.

 

The test comes to a conclusion only when it has been proven that the product has not supported the microbial growth.

 

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