Does Stress Sweat Smell the Same as Exercise Sweat?

Does sweat produced under stress smell the same as sweat produced during exercise? In a 2013 study comparing sweat from the same men, samples collected during stress were rated as more intense in odor than exercise samples, even though less sweat was collected.

Alongside this comparison, the main purpose of the study was to determine whether three forms of unperfumed antiperspirant, a roll-on, a stick, and an aerosol, could reduce sweating and odor under stress. Assessments were made 48 hours after the last application following several days of use.

Creating stress with an interview and mental arithmetic

The researchers used the Trier Social Stress Test (TSST), which combines a mock interview with mental arithmetic. After brief preparation, participants delivered a speech simulating a job interview before a panel, then counted backward from 2023 in steps of 17. If they made a mistake, they had to start again. The task lasted 15 minutes in total.

Heart rate, salivary cortisol, and participants’ questionnaire responses were used to confirm that a stress response had occurred. Heart rate and cortisol rose in each formulation group, and participants reported feeling stressed. The untreated underarms produced an average of about 0.3 g of sweat during the 15-minute task.

Ninety-five people were recruited for the stress study. After exclusions for deviations in application quantity, displaced sweat pads, outliers, and other reasons, formulation efficacy was analyzed in 84 participants. There were 28 participants per formulation; not everyone used all three products. The pooled analysis of untreated-underarm sweat used 88 participants, a different number from the formulation-efficacy analysis.

Applying the product to one underarm and comparing it with the other

Healthy, nonsmoking women and men followed standardized washing and product-use procedures before a test product was applied to one underarm. The treated side was randomly assigned, and the other side was left untreated. The roll-on was used on four consecutive days, and the stick and aerosol on five consecutive days. The stress task took place 48 hours after the last application.

All three formulations contained antiperspirant ingredients such as aluminum salts and zinc compounds, but no fragrance. There were also separate aerosol formulations for men and women. These were not identical formulas presented in different forms: ingredients and application quantities differed too.

Sweat was collected on cotton pads secured under the arms and measured by the increase in pad weight. For odor assessment, frozen pads were returned to room temperature and rated by six trained assessors on a 0–5 scale.

All three formulations reduced sweat, with one exception in odor reduction

During the stress task, all three formulations reduced sweat relative to the untreated side in both sexes. Averaging individual percentage reductions, the roll-on reduced sweat by 51% in men and 55% in women, the stick by 58% and 50%, and the aerosol by 33% and 50%. Individual differences were large, and sex differences within each formulation group were not significant.

Odor scores were also lower on the treated side in all three male groups and in the female roll-on and aerosol groups. The exception was the female stick group, where the difference between mean scores of 1.86 untreated and 1.74 treated was not significant. The authors suggested that the relatively weak odor on the untreated side in this group might explain the result.

The findings show an effect on stress-induced sweat 48 hours after the last use under the tested formulations and application procedures. This was not a fragrance-masking study, but neither did it separate sweat reduction from effects on bacteria. The numerical results alone cannot establish a general ranking of application forms.

Testing the roll-on against heat-induced sweating

A separate heat study tested the roll-on as a representative formulation. Eighty-two participants were recruited and 76 completed the study. After spending 40 minutes in a room at approximately 38°C, sweat was collected for 20 minutes. The product was again applied for four days and measurements made 48 hours after the last application.

About 1 g of sweat was collected from the untreated side, and sweat was significantly lower on the treated side in both sexes. The overall mean of individual percentage reductions was 28%. Participants, environmental conditions, and collection times differed from the stress task, so directly comparing the percentages cannot tell us how many times more effective the product was against one type of sweating than the other.

Stress sweat smelled stronger despite a smaller quantity

Another comparison collected sweat from 19 men during the stress task and cycle-ergometer exercise. Exercise took place before product application began, with sweat collected over the last 15 minutes of the 25-minute session. Comparing sweat from the untreated side within the same individuals, the mean was 0.601 g during exercise and 0.402 g during stress.

However, trained-panel odor intensity was significantly higher during stress: 2.77 versus 2.13 during exercise. Greater sweat weight did not necessarily mean stronger odor.

Twenty untrained women and men also tried to identify the stress sample from paired samples belonging to the same donor. Mean accuracy was about 56%, slightly above chance. The task allowed participants to answer that they could not distinguish the samples. This does not establish that people can accurately smell others’ stress in everyday life, but supports the view that sweat from the two situations did not have identical sensory characteristics.

The findings concern particular formulations and test conditions

The stress study was open-label and compared treatment with no treatment. The authors noted that pad attachment could affect sweat recovery and that some participants were excluded from the analyses.

The chemical composition of sweat odor and the skin bacteria were not directly analyzed, so the study did not identify the molecules responsible for the stronger stress odor. The results do not guarantee effectiveness for every commercial antiperspirant or any pattern of use; they are best read as evaluations of the formulations tested.

Summary

In the same men, sweat collected during stress was rated as more intense in odor than exercise sweat despite its smaller quantity. Sweat quantity alone could not fully explain perceived odor.

In the formulation trials, three unperfumed antiperspirants used for several days reduced stress-induced sweat relative to untreated underarms 48 hours after the final application. Odor was also lower in most groups, although not significantly in the female stick group. A separate heat study confirmed sweat reduction with the roll-on, illustrating the value of distinguishing the situation that triggers sweating and separately assessing both sweat quantity and odor.

Research funding and affiliations: Beiersdorf funded the research in full, and all six authors were affiliated with the company at the time. No separate conflict-of-interest declaration was identified.

Reference

Schmidt-Rose T, Lehmbeck F, Bürger A, Windisch B, Keyhani R, Max H. Efficient sweat reduction of three different antiperspirant application forms during stress-induced sweating. International Journal of Cosmetic Science. 2013;35:622–631. doi:10.1111/ics.12086