Testing the effectiveness of deodorants (2025)

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Interviewer: Welcome Frederike and Marianne. How can you judge the effectiveness of deodorants and antiperspirants?

• FREDERIKE: Well, we measure the effectiveness either in terms of odour reduction or in terms of sweat reduction.
  
• MARIANNE: To determine the amount of sweat, we carry out gravimetric measurements after sweat induction under standardised conditions, for example in our warming room, which we perform in accordance with FDA and Clearcast guidelines. The underarm sweat is collected with a cotton pad and then weighed. The amount of sweat produced is then compared with the initial value and with a control. We also offer ATS (Anti-Transpirant Screening), which is performed on the subject's back and can test up to 8 formulations at once. In this case, sweating is induced in the sauna.

Interviewer: So we ask the participants to sit in the sauna to make them sweat! I was wondering whether we ask the participants to exercise or not, but the sauna is much more relaxing.

• MARIANNE: Yes, participants sit in the sauna for 15-20 minutes, but there are other ways to stimulate sweating; it depends on what the client is looking for. There are different types of sweating that result from different metabolic situations! For example, we can sweat passively in the sauna or in the warming room, but also actively over a longer period of time on a cross trainer or an exercise bike. We once conducted a study in which the customer wanted to investigate the effectiveness of his product against stress-induced sweating.

Interviewer: A stress test! How did you do it?

• MARIANNE: We had a psychologist come and interview our test subjects with emotional questions. That worked really well!

Interviewer: I've always wondered why we sweat when we're stressed; maybe there's an evolutionary link between survival and odour! Speaking of odour, how do you measure body odour when you sweat?

• MARIANNE: Our standard is the underarm deodorant test. This is conducted by our odour judges, also known unofficially as ‘sniffers’; they perform ‘sniff tests’ (or odour intensity ratings) by smelling the subject's armpit and rating the intensity of the odour. We have 2 approaches to odour scoring: an analogue scale, which is a little easier for the judges to handle as they only score against the untreated area - or alternatively we use an ordinal scale from 0-5 to categorise odour intensity in one step, which requires a little more training. However, if you achieve an improvement with your deodorant on the ordinal scale, you can be sure that the consumer will notice the effect in the real world.
  
• FREDERIKE: Yes, and it is important to note that the noses of the odour judges are first tested with isovaleric acid, one of the odour-causing components of sweat, to identify those judges who are unable to assess the intensity of this component on the day, perhaps due to a cold, and therefore need to be replaced. The judges then smell both armpits before applying the deodorant and assess this, then the subject applies the test product to one armpit and the judges then perform a second sniff test on each armpit. In this way, we can compare treated and untreated armpits before and after application of the product to assess the effectiveness of the deodorant.

Interviewer: So who are these talented people who make up our olfactory jury, and can anyone become one of them?

• MARIANNE: Well, it's not as if everyone can say: ‘OK, today I want to become an odour judge’. Not everyone has the necessary ability to recognise the intensity of odours.
  
• FREDERIKE: And even if they can, they need to be trained regularly. They need to be trained to a recognised standard. For example, our odour judges are trained once a year and then again immediately before each study to ensure that their noses are calibrated, so to speak.
  Our odour judges are trained by Olfasense, a company based in Kiel that specialises in odour measurements. An Olfasense trainer comes to us with an Olfactometer and trains our judges on site.

Interviewer: And how is this ‘odour judge training’ carried out?

• MARIANNE: There are some standard substances that are very similar to those found in sweat. The judges have to smell them and then rate the intensity of the odour according to what they perceive, and this is then compared with what the instrument (olfactometer) measures. This process is repeated until the two values match; at the end of the training, the judge's assessment matches the instrumental measurement. Firstly, the sensitivity of the judge's nose is assessed to determine whether they are suitable for this particular study, i.e. whether their sense of smell is sensitive enough to perceive these substances at different intensities.

• FREDERIKE: Yes, the sensitivity of the judge's nose is first determined to n-butanol and a number of other sweat odours. We find the minimum concentration that can be detected by the judge and then they have to assess the concentrations. This year I had the opportunity to attend the training and it's really hard, it sounds easy but it's not! Especially the n-butanol is a real challenge.
  
• MARIANNE: Although all this training sounds like a big investment and certainly brings additional challenges to these studies, it is essential to deliver high quality results to our clients.

Interviewer: How easy is it to find odour assessors? I can't imagine there are too many people willing to spend their days smelling these... let's say... less fragrant odours.

• FREDERIKE: It's not that easy. Not only do they have to have the desire to do it, they have to have, as Marianne said, a good feel for it; and they also have to be very flexible, because they don't just come for 5 or 10 minutes, they're here for up to 4 hours at a time, maybe 3 or 4 days a week; sometimes in the afternoon, sometimes in the morning. And we also need very polite and friendly people as judges, because they obviously work very closely with the participants in the study.
  
• MARIANNE: As for people's natural ability to recognise different smells so accurately, perfume developers are also very rare. Not many people have sensitive noses for such a complicated odour analysis.

Interviewer: If I'm right, do the judges smell directly at the armpit? Or do we collect the sweat and its odour in a pad?

• FREDERIKE: The judges smell directly at the armpit. There is a wall between the subjects and the judges to avoid any bias; and there is a small hole in the wall at the level of the armpit through which the judge can smell the armpit.

• MARIANNE: There are of course other study designs, for example, if body odour is to be assessed after a period of daily activity, subjects can wear a pad to collect the sweat odour and the pad is returned and then placed in a sealed vial for the judges to come a little later to assess the odour. The training of the judges remains the same. Only the method of odour determination or sample preparation would be different in this case. We can now offer this since we are part of the SGS. Both are valid, published methods, but the direct sniffing approach means that you can judge what is going on on the skin. Ultimately, the direct sniff method is closer to the consumer's perception of the product. Nevertheless, both methods provide valid results for substantiating claims.
  

Interviewer: What types of studies with sniffers are most common? Are these only studies on underarm deodorants?

• MARIANNE: Well, sweat odour evaluations are the most common. In addition to evaluating body odour to assess the effectiveness of deodorants, judges may also evaluate the fragrance component of the test product as an additional parameter, i.e. they must indicate whether they can perceive the fragrance and whether they find it pleasant. Sometimes we also use odour experts to evaluate mouth or food odour. Of course, both require different training than body odour studies.

Interviewer: And what would be the most unique study you have conducted so far?

• FREDERIKE: Well, a study planned for next year will look at incontinence pads and their ability to bind odour. Our odour judges will be involved in this study.

Interviewer: Ok, I was thinking about getting my sense of smell tested to see if I have what it takes to be an odour judge, but now I'm reconsidering. Which makes me think - do we always use odour judges for these odour assessment studies, or are there alternative methods of odour detection?

• FREDERIKE: There is a device that can be used for oral odour studies.
  
• MARIANNE: Yes, the OralChroma. You take a breath sample with a syringe, which is then injected into the OralChroma, and this device then detects the various odours. But in general, we have not found an alternative method that can reliably reproduce what the odour judges can detect. Therefore, when we offer these alternative methods, we usually work with odour judges and use both methods to complement each other.
  

Interviewer: It's good to know that humans are not being replaced by technology in all areas! Many thanks to you both and much respect to our talented odour judges!