Hair and scalp treatment has always been a cosmetic field of choice.
Instrument of seduction for the female sex and representative element of vigor and youth for the male, a beautiful "flowing" hair always catches the attention. Hair care is an element of individual well-being but also of social communication.
The formulator of cosmetics for the hair and scalp must keep in mind that they act on a complex physiological system. Structured like a cylinder formed by coaxial layers, the hair is made up of the stem, the external visible part and the internal one, rooted in the skin, formed by bulb and matrix..
The stem is made up of three sections, with cells containing different types of keratin, the basic protein of the hair, nails and of the stratum corneum of the epidermis. The internal parts of the hair, matrix and bulb, are made up of continuous cells reproductive activities, which multiply by moving upwards, giving rise to the stem. Surrounding the bulb are the capillary blood vessels, from which the cells draw nutrients.
The sebaceous glands, organs of lubrication, are also grafted into it.
The well-being of hair
Hair has a life cycle that alternates between phases of activity and productive rest, allowing gradual and continuous renewal. In fact, the cycle of each bulb appears to be independent of the surrounding bulbs and, unlike the seasonal moulting of animals, humans under normal conditions do not change their hair all at once. The wellbeing of the hair derives not only from a healthy organism, but also from the balance of the scalp, its secretions and blood circulation, as well as the resident microflora of bacteria, yeasts and fungi. The properties of the hair shaft, now made up of non-viable cells, depend on both environmental exposure and cosmetic treatments
In vivo instrumental evaluations
Anti-dandruff efficacy
Sebum normalizing efficacy
Efficacy of treatment for strenghtening and reinvigorating the hair (pull test e wash test)
Efficacy of treatment for preventing the hair loss-phototrichogram tecnique
Evaluations of harmlessness
Open and/or occlusive patch test on sensitive and/or normal skin
Human Repeated Insult Patch Test - HRIPT
Photopatch Test
Predictive test for hypoallergenicity
In-vitro instrumental evaluation
As part of the evaluation of the efficacy of products intended for the hair, it is possible to carry out a series of in-vitro tests, which do not involve the study on volunteers, but which are nevertheless performed on strands of human hair or on yak hair. The choice of hair type/color on which to perform the test can be made according to your needs.
The purpose of the test is the instrumental quantification of the color permanence on the hair, after repeated washings, comparing treated strands and control strands. The instrument used is the colorimeter (measurements in the CIELab chromatic space). The measurement system reads the L*, a* and b* values that define a point in the color space. The data are processed statistically and, when necessary, compared by t-test. The following parameters are evaluated: L* and ΔL for coverage; C and ΔC for saturation; ΔE for the overall color variation
Curl retention: the aim of the test is the quantitative evaluation of the elasticity of treated hair in comparison with hair not treated with a specific product. A weight is applied to the hair strands that have been previously straightened by means of a curler. The elongation of the strands is measured at successive times using graph paper. A statistical comparison of the data is carried out by means of a t-test to assess the significance of the results
Hydratation: The purpose of the test is to quantify the level of hydration of treated hair strands compared to untreated hair. A gravimetric method is used, by means of an analytical balance, based on the capacity of the hair strands to maintain a good level of hydration in predefined conditions of temperature and humidity. A statistical evaluation of the data obtained by t-test is carried out
Tensile strenght: the purpose of the test is to evaluate the weight required to break a single hair under the action of a constant force. The test is conducted by comparing strands of damaged, untreated and treated hair. For the measurement of the breaking load is used the Texture Analyzer TX-700 (Lamy Rheology), equipped with accessory "Noodle Tensile Fixture" to which is fixed the hair. The test is performed on 20 or more hairs extracted from the strand; the instrument provides the applied force (in g) required to break the hair; statistical comparison of the data is performed
Combability: with the same instrument (Texture Analyzer TX-700) it is possible to evaluate the force required to comb a strand of both dry and wet hair under the action of a constant force. The test is conducted by comparing strands of damaged, untreated and treated hair. The test is carried out on several strands; the instrument provides the resistance produced by the strand to the passage of a comb; a statistical comparison of the data is carried out
Sensory evaluations
Sensory analysis is a scientific discipline that identifies, measures and interprets the stimuli evoked by the use of a product and transmitted to the sense organs. It uses a group of panelists trained to perceive and quantify the sensory stimuli generated by the interaction between skin and product. Furthermore, the user's judgement is collected by filling in a questionnaire evaluating the perceived performance and pleasantness of the product.
Paired comparison test
Ranking test
Triangle test
Quantitative descriptive analysis - QDA
Subjective evaluation
Clinical evaluations
Complementing the instrumental assessments are the clinical evaluations performed by the medical specialist (eg. dermatologist, oculist) who objectively assesses the improvement in skin parameters using scores and scales.
