Beyond Masking: A New Focus on Scalp Odor Prevention

While body odor is a well-understood and extensively addressed consumer concern in the personal care industry, scalp odor is a common issue, on which not much scientific content can be found yet. This hair and scalp condition, characterized by a rancid, non-fresh odor, is often a source for discomfort, impacting consumer confidence. 

The global hair and scalp care market is valued approximately USD 93.9 billion in 2025 and projected to grow to $129.4 billion by 2030, reflecting a historic CAGR of 4.3% from 2020-2025 and a projected annual growth of 5.6% from 2025-2030¹. In addition other market reports indicate a CAGR of 11.5% specifically for the global scalp deodorant market, which was estimated $420 million in 2024 and projected to reach USD 1.14 billion by 2033². This strong growth is derived from factors including rising consumer awareness around personal hygiene, increased interest in hair and scalp health and partly even by the "skinification" of hair care, a trend where consumers apply the same diligence and ingredient-focus to their scalp as they do to their facial skin. 

The causes of scalp odor are distinct from common body odor that typically originates mostly from the armpits with a high concentration of apocrine glands. While the armpit is subject to daily skincare regimens, the scalp may be treated on a much lesser frequency and often only as a side-effect while washing the hair. Here also lies a further difference: hair shafts tend to absorb external odors like a sponge, thus absorbing cigarette smoke, fireplace fumes or strong kitchen odors. Scalp odor, on the other hand, is primarily linked to the buildup and subsequent oxidation of sebum, sweat and dead skin cells, creating a rancid, lipidic profile. This often interacts with the odor acquired by the hair shafts. 

Due to the big advances in microbiome research over the last 15 years, recent research often focused on odor formation derived from bacterial degradation of various precursors^3,4. In parallel, odor formation from sebum excluding bacterial activity is underrepresented in literature. Sebum itself is lipid-rich and generally consists of sterols, and often esterified fatty acids⁵. It is secreted by sebaceous glands, which can be found in all parts of the human body, but concentrate on the head and upper torso⁶. While nearly all mammals secrete sebum⁷, its composition is highly species-specific for each member of this versatile community. In humans, major components are squalene and sapienic acid⁸. Odorous molecules from abiotic degradation are often the result of oxidation processes, for example yielding ketones and aldehydes like acetone, sulcatone, geranylacetone and 4-oxopentanal derived from squalene⁹. On the other hand, aldehydes and volatile organic acids are reported as cleavage products derived from unsaturated fatty acids like sapienic acid¹⁰. Overall, not many scientific reports on scalp odor exist in literature today.  

Hair odor changes frequently depending on the acquired smells, but scalp odor commonly builds over time. In this review, we will focus particularly on the scalp. Scalp odor is favored by various factors, but may be grouped into three major causes, driving consumers to seek for solutions that reduce bad odors: 

• Complex Hair Care Routines: Certain consumer groups do not wash their hair with the same frequency as they follow other body hygiene principles. For example, ethnic hair types require time-consuming cleansing routines, or it may simply be a personal preference. This may lead to an accumulation of sebum and residues on the scalp, creating a favorable environment for odor development and bacterial growth. These markets primarily seek leave on scalp deodorant options, because rinse-off procedures are not applied frequently.
• Hot Climate and Head Coverings: In other hot and humid regions, or for individuals who regularly wear head coverings like hijabs, helmets or hats, the scalp is often occluded. This traps heat and sweat, accelerating odor formation and microbial growth. In major markets like South East Asia, the predominant hair color is dark, making flakes easily visible. Thus solutions for dandruff are closely connected. This market favors rinse-off solutions that solve odor and flaking both in one go.
• Active Lifestyles: People highly engaged in sports and frequent physical activity with increased sweating rates may not wash their hair after every session. Especially for indoor sports, odor concerns may appear creating an increased demand for solutions that offer consumers lasting freshness. It could be either leave-on or rinse-off. 

Until today, the cosmetic market has predominantly addressed scalp odor with absorption technologies or fragrance-based masking solutions. However, both options merely cover up the malodor temporarily without addressing its root cause. Technical progress in detection methodologies is expected to deliver better understanding of what exactly forms malodor to cover this gap. In this report, however, we would like to present our findings from exploring two different antimicrobial technologies for odor prevention. By conducting two separate in-vivo studies we have explored scalp odor prevention, setting the basis for more advanced in-detailed studies in the future.

Study 1: Leave-on Scalp Deodorant

This study was designed to assess the effectiveness in scalp odor reduction by application of a light, leave-on scalp deodorant (see Table 1) comprising 0.3% propanediol caprate¹¹ vs untreated. The in-vivo sniffing study was conducted in Brazil with a panel of 20 male and female participants at 18-60 years of age and of Fitzgerald phototypes II, III, IV, V and VI. All subjects claimed to have problems with scalp odor. 

The study protocol required the subjects to carry out four visits at the test institute on four subsequent days. Participants were not allowed to wash their hair except one instructed wash before the study started. Upon the first visit, a neutral shampoo was provided. During the following one-day conditioning phase, the subjects were asked to wash their hair only with this shampoo and at least 24 hours before the first assessment in the next visit. 

The next day, during Visit 2, the participants first underwent an 80-minute, 38°C sauna session to simulate a hot climate. A baseline odor assessment (24 hours after washing after the sauna session) was then performed by three trained experts using a direct-sniffing method on a scale of 0 (no odor) to 10 (extremely strong odor). Following this, a single application of the test product was conducted. 

Visit 3 started with another 80-minute sauna session, followed by the second odor assessment (24 hours after product application, 48 hours after washing). During Visit 4, a final 80-minute sauna session was followed by the final odor assessment (48h after product application, 72 hours after washing). Thus in summary, hair was washed only once before the start of the study, and the test product was only applied once on day 2 after the first sauna session. 

Figure 1 - Scalp odor reduction 24h/48h after single application of an un-fragranced scalp deodorant comprising 0.3% propanediol caprateCourtesy of Symrise

The leave-on scalp deodorant demonstrated a statistically significant reduction in scalp odor (p<0.05) compared to baseline on both assessed time points (24h, 48h). The average scalp odor was reduced by 17% at 24 hours after product application and by 10% at 48 hours respectively ( see Figure 1). Notably, 100% of the subjects, both male and female, all ages and all 5 phototypes tested, experienced a reduction in scalp odor 48 hours after a single product application. Considering the simplistic unperfumed formula of the light leave-on scalp deodorant comprising only 0.3% of a deodorant molecule featuring antimicrobial properties but no masking technology, the odor prevention result observed is even more remarkable compared to the plain odor reduction. In consequence, starting from product application, further odor formation was obviously blocked and an even better result would be expected upon product application right after showering in future studies upon modification of the protocol. 

Study 2: Scalp Odor Reduction From Rinse-off Anti-Dandruff Shampoo

The second study was conducted in Indonesia. An anti-dandruff shampoo containing an active blend¹² comprising decylene glycol and piroctone olamine in 1,2-hexanediol and glycerin was explored for its ability to control scalp malodor at 1.5% dosage.

This study assessed the efficacy of a simple shampoo with 1.5% of the active blend against a placebo (see Table 2) on 12 male and female subjects over a nine-day period, with hair washed every two days at home by the subjects themselves. Scalp odor was evaluated by eight trained assessors on a 0-10 scale at multiple time points (see Figure 2), each assessor evaluating all subjects and all time points: right before washing (T0), immediately after washing (T1), 4 hours after washing (T4) and 8 hours after washing (T8).

Figure 2 - Scalp odor reduction by repeated washing with an anti-dandruff shampoo containing an active blend of decylene glycol and piroctone olamine in 1,2-hexanediol and glycerin vs placebo shampoo.Courtesy of Symrise

The test shampoo containing 1.5% active blend delivered statistically significant scalp malodor reduction vs baseline and compared to placebo (p<0.05) after multiple uses. On day one after single shampooing, the malodor score for the active shampoo dropped significantly from a baseline of 7.3 (T0) to 6.0 (T1) and remained significantly lower than the baseline for at least 8 hours. On day nine, after several days of application the deodorizing effect was even more pronounced. The pre-wash odor level was rated 6.1 (T0) on Day 9 and showed a lower score than the initial pre-wash score of 7.1 on Day 1, indicating a cumulative trend. The scalp's odor eight hours after the final wash (T8, Day 9), was compared to the odor before the first wash (T0, Day 1)  and showed a statistically significant decrease in intensity from 7.3 to 3.6 on the 0 to 10 scale for the active shampoo vs a reduction from 7.1 to 4.6 for the placebo shampoo. 

Discussion

These two studies demonstrate that scalp malodor can be effectively managed through targeted, preventive cosmetic technologies with an antimicrobial effect rather than relying solely on fragrance masking. The consumer trend towards scalp health and solution-driven products underscores the need for such innovations.  

The leave-on study using propanediol caprate highlights a powerful intervention for consumers who do not wash their hair daily. Propanediol caprate is known for its antimicrobial deodorant properties and the ability to provide strong odor protection^13,14. The significant odor reduction is particularly noteworthy given the challenging test protocol; the product was applied 24 hours after shampooing, a moment at which sebum and microorganisms already were in an advanced state. This test is primarily designed for today´s focus on masking technology. It is reasonable to hypothesize that the results could be even more impressive if the product was applied to a clean scalp immediately after washing, to prevent the odor-formation cascade from beginning.

Rinse-off study 2 using the active blend¹² addresses the needs of consumers in hot, humid climates and in connection with dandruff, which often co-exist with scalp malodor. The lasting effect, which shows a cumulative reduction in scalp odor over 9 days, proves that regular use can help maintain a fresher odorless scalp environment. The ingredient blend provides a significant benefit in combining dandruff control and scalp odor prevention from shampoo use for individuals wearing head coverings or those with active lifestyles.

Conclusion

We successfully explored scalp odor prevention by two independent in-vivo studies conducted at external institutes in Brazil and Indonesia. The findings confirm that scalp malodor, an under-addressed consumer concern, can be significantly reduced by antimicrobial technologies.

It is obvious from our market observation and the nature of available testing protocols that the industry was, until now, primarily relying on odor-masking approaches. Thus addressing the underlying biological causes of scalp odor is a new field to play. The technologies presented here represent a paradigm shift towards odor prevention.

We encourage the scientific community and cosmetic formulators to look beyond mere odor masking. Especially more research on sebum degradation is expected to help uncover new distinct pathways of odor formation¹⁴. By focusing on prevention, we can offer consumers more effective, longer-lasting, and scientifically backed solutions for scalp confidence.

References

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