60 BODY CARE
application of the antiperspirant. The reduction in sweat compared to untreated axilla is then determined. Testing may be done at various time points to determine the duration of the antiperspirant effect (e.g. 24-hour protection). Another well-known, although less used, method is based on the staining of the sweat water based on the iodine starch reaction.2 Water droplets will appear as blue dots. Photographs can be taken to count the number of active sweat glands and quantify sweat production. Visualizing the distribution and number of sweat droplets is one advantage of the iodine starch technique. These methods are not only useful for
the evaluation of the efficacy of cosmetic antiperspirants but also for the assessment of primary axillary hyperhidrosis, a common conditions characterized by an excessive sweat production.3
In vivo assessment of deodorants With regards to testing deodorants efficacy, there are several scientifically validated methods and frameworks, involving either sensory assessments or instrumental measurements. Since the purpose of deodorants is to mask or eliminate malodour, in use test is obviously an interesting approach. Products are tested by a panel of subject
over a period of time who will score or answer questions related to the control of body odour, providing a real consumer perspective on the efficacy of the deodorant under investigation. However the standard for testing the effectiveness of deodorants is to perform a sensory evaluation of axillary odours with a group of trained assessors. This sensory method became known under the name of ‘sniff test’.2,4
This is carried out
under controlled conditions while allowing the participating subjects to carry on their daily activities; the objective being to be close to the real conditions of usage of deodorants. As for all kinds of sensory evaluation, it
is critical to select the odour assessors or sniffers with great care to limit the subjective nature of such an approach. Not everybody is qualified, or motivated enough, to become a performing sniffer capable of detecting subtle odour differences. Therefore, training and qualification of sensory assessors is of the uppermost importance. An excellent screening and training protocol has been published that can serve as a basis to qualify odour assessors before.5 To further increase the reliability of sniff
tests, some guidelines have been proposed.2,6 In particular, the American Society for Testing and Materials (ASTM) has a standard for testing deodorants.6
When performing a sniff
test based on ASTM E1207 standard, testing must be done in an environment where temperature, hygrometry and background odours are controlled. The test starts with a pre-treatment
conditioning period during which subjects are asked to abstain from the use of all deodorants, antiperspirants, perfumed soaps on the armpits. For the main test
PERSONAL CARE April 2025
period, axillas are washed with an unscented cleansing product. Baseline odour evaluations are performed by four trained assessors. Then, subjects are issued T-shirts that
have been washed with perfume-free washing powder. After a defined period of time (e.g. 8 or 24 hours) while the subjects have their normal daily routine, odours are assessed by the sniffers by smelling directly at the axillary vaults of the subjects. In order to be less embarrassing for
both the volunteers and the assessors, the evaluation can be done on pads that collected sweat from the armpits. The grading of sweat odour intensities is done based on a rating scale ranging from 0 (no sweat odour) to 5 (very strong sweat odour). The detection, identification and
quantification of smells can be done using instrumental olfactometry. This involves equipment such as gas chromatographs combined with mass spectrometers or electronic noses to analyze the chemical composition of odours. Data provided by these methods are more precise since they can identify specific molecules responsible for particular smells. Yet they do not replace sniff tests that are close to the consumer perception of body malodours.
Deodorants are typically evaluated for their
ability to neutralize or mask odours. It is also interesting to check how well they perform in comparison to untreated skin, to placebos or to benchmarks. They are also often tested to measure how long they remain effective in order to claim 24- or 48-hour protection.
In vivo assessment of hair removal efficacy Unwanted hair in the axillae is a common cosmetic concern, either for purely aesthetic reasons but also because the presence of hair favours the development of malodours as previously discussed. Many hair removal treatments and procedures are available, leading to short-term (shaving, waxing, depilatory creams) or long-term/permanent results (laser, electrolysis). Similarly to hair from the scalp, axillary hair
goes through four phases. The anagen phase is the longest and corresponds to the active growth phase. It is followed by a transition phase called catagen, lasting approximately two weeks. Then, the telogen phase follows where hair stops growing and rests. Lastly, the exogen phase is when the
shedding of hair happens. Telogen hair is pushed out as the new hair starts to grow. This cycle
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