Body Odor Research Articles

Bacillus xiamenensis Inhibits the Growth of Moraxella osloensis by Producing Indole-3-Carboxaldehyde.

Moraxella osloensis, a gram-negative rod-shaped bacterium found on human skin, produces 4-methyl-3-hexenoic acid, contributing to clothing and body malodor. M. osloensis is resistant to UV light, drying, and antimicrobials, making its eradication challenging. As the skin is low in nutrients, commensal bacteria compete for resources and use diverse strategies to inhibit their competitors. Therefore, skin-derived bacteria that exhibited growth-inhibitory activity against M. osloensis were searched. Screening skin-derived bacteria using a coculture halo assay revealed that Bacillus xiamenensis formed an inhibition zone with M. osloensis. Coculture plates were extracted with ethyl acetate and fractionated using a silica gel column and preparative thin-layer chromatography to isolate the active compound from the B. xiamenensis metabolites. Nuclear magnetic resonance spectroscopy identified the active compound as indole-3-carboxaldehyde, which has low toxicity in humans. At soluble concentrations, indole-3-carboxaldehyde does not inhibit the growth of other bacteria, such as Staphylococcus aureus, Escherichia coli, and Bacillus subtilis, suggesting M. osloensis is highly sensitive to indole-3-carboxaldehyde. These findings highlight B. xiamenensis as a promising candidate for the development of a skin probiotic to promote skin health and combat malodor-causing bacteria.

Case Study on Management of Overweight (Sthoulya) through Ayurveda

ABSTRACT Modernization, affluence, and advancements in science and technology have led to increasingly sedentary lifestyles. This unintentionally invites a range of health issues, one of which is Sthoulya (overweight), which can affect physical, mental, and social health. Sthoulya refers to an individual who has excessive fat and flesh accumulation, causing a disproportional enlargement of the buttocks, belly, and breasts without a corresponding increase in energy. A 38-year-old female patient presented with weight gain, excessive hunger, sleep and sweating, lack of enthusiasm, and bad body odor. Before and after therapy, the patient was assessed for subjective and objective characteristics. There was an improvement in subjective parameters, anthropometric measurements, body mass index (BMI), and body weight after treatment. The combination therapy comprising Tryushanadi Guggul, Udvartan with Vacha Churna, and Peti Sweda demonstrated effectiveness in improving the lipid profile and anthropometric measurements of the patient over a 30-day treatment period.

Deodorising Garlic Body Odour by Ingesting Natural Food Additives Containing Phenolic Compounds and Polyphenol Oxidase

Garlic consumption is a well-known cause of unpleasant breath and body odour, with volatile organosulfur compounds, such as diallyl disulfide (DADS) and allyl methyl sulfide (AMS) responsible for the characteristic odour. Certain foods that are rich in polyphenols (PPs) and polyphenol oxidase (PPO) are known to deodorise garlic breath. However, no study into garlic body odour has been reported owing to the very low amounts of emitted volatile organosulfur compounds. Herein, we aimed to demonstrate the effects of ingesting natural food additives rich in both PPs and PPO on the emissions of skin-derived DADS and AMS using a passive flux sampler in conjunction with gas chromatography–mass spectrometry. Three healthy male subjects were subjected to garlic-consumption testing, with all subjects commonly observed to exhibit remarkably higher dermal DADS- and AMS-emission fluxes after consuming 45 g of cooked garlic, which then gradually decreased toward their initial baseline levels. In comparison, remarkably lower emission fluxes of both organosulfur compounds were observed after consuming a natural food additive following garlic consumption in a dose-dependent manner. The optimal amount of ingested natural food additive required to reduce garlic body odour was found to be 1–2 g. Considering the metabolic pathway associated with garlic-derived sulfur compounds and elimination reactions involving PPs and PPO, allyl mercaptan is likely to be a key substance involved in reducing garlic body odour through the ingestion of natural food additives.

The Impact of Body Odors on Sexual Attraction and Partner Selection: A Review of Cisgender Homosexual Men and Women.

This study examined the role of odors in sexual attraction and partner selection among non-heterosexual individuals. We searched using MESH terms in databases including PubMed, Embase, Scopus, Web of Science, Cochrane Central Register of Controlled Trials, CINAHL, and Clinical Trials. We focused on experimental or quasi-experimental studies where olfactory cues were used in partner selection. The studies had to identify participants' sexual orientation and include heterosexuals for comparison. Seven studies, published between 2005 and 2014, involving 345 participants (Mean age, 27.09years), met the criteria. Results suggest that sexual orientation affects both preference for and production of human body odors and that human body odors appear to provide cues about the sex and sexual orientation of potential partners. Most participants were male, limiting conclusions about the role of pheromones in attraction among non-heterosexual women.

‘I have normalised being treated differently’. Analysis of the experiences of foreign students in Physical Education

ABSTRACT Purpose The aim of the study is to analyse the experiences of 7 students (4 girls and 3 boys) from different continents (Africa, Asia and South America) in Physical Education, in order to know to what extent, they have perceived racism. Their guardians also participated. All the students have experienced their compulsory schooling in Spain. Methods The research is framed under the theory of culturally relevant pedagogy. A qualitative approach is used in which three categories of analysis are established: (a) Perception of social discrimination; (b) Effect on self-esteem and emotional implications; (c) Learning limitations in Physical Education. Interviews with students and focus groups with guardians, where the data collection techniques are/were used. Findings & conclusions The results show how students have suffered covert racism in the classroom, specifically in Physical Education, observed in a diversity of behaviours and actions linked to the colour of their skin, their accent, their physical features and even their body odour. This, despite their subliminal acceptance of it, has generated frustration, powerlessness and diminished self-esteem, as well as a bad relationship with the subject. Guardians recognize the experience of these forms of discrimination and emphasize that racism still exists in society and in schools, and that there is a lack of mechanisms and procedures to eradicate it. It is essential to continue researching how to approach a teaching of Physical Education that moves away from any type of discrimination, but this article is already a first step in giving a voice to those who suffer from it.

Sniffing out a solution: How emotional body odors can improve mindfulness therapy for social anxiety

BackgroundHuman body odors (BOs) serve as an effective means of social communication, with individuals exposed to emotional BOs experiencing a partial replication of the sender's affective state. This phenomenon may be particularly relevant in conditions where social interactions are impaired, such as social anxiety. Our study aimed to investigate if emotional human BOs could augment the benefits of mindfulness-based interventions. MethodsWe enrolled 48 women with social anxiety symptoms and assigned them to groups exposed to happiness BO, fear BO, or clean air. Participants engaged in mindfulness practice over two consecutive days, which included breathing, meditation, and relaxation exercises. During these interventions, the odor specific to each group was presented. Affective symptoms were assessed at the beginning and end of each day, with heart rate variability (HRV) and skin conductance level (SCL) recorded during the intervention. ResultsSelf-reported anxiety level revealed a significant reduction in anxiety on the second day for both happiness and fear conditions, but not for the clean air group. However, on a physiological level, fear BO exposure compared to clean air led to decreased HRV, indicating that fear BO may induce a less physiological relaxed state. No significant differences were observed in SCL between odor conditions. ConclusionsThese findings suggest that exposure to BOs triggers the perception of a “social presence”, improving the ecological validity of a psychological treatment. If replicated and expanded, these findings could pave the way for using BOs as catalysts in existing therapies.

Identification of a staphylococcal dipeptidase involved in the production of human body odor

The production of human body odour is the result of the action of commensal skin bacteria, including Staphylococcus hominis, acting to biotransform odourless apocrine gland secretions into volatile chemicals like thioalcohols such as 3-methyl-3-sulphanylhexan-1-ol (3M3SH). As the secreted odour precursor Cys-Gly-3M3SH contains a dipeptide, yet the final enzyme in the biotransformation pathway only functions on Cys-3M3SH, we sought to identify the remaining step in this human-adapted biochemical pathway using a novel coupled enzyme assay. Purification of this activity from S. hominis extracts led to the identification of the M20A-family PepV peptidase (ShPepV) as the primary Cys-Gly-3M3SH dipeptidase. To establish whether this was a primary substrate for PepV, the recombinant protein was purified and demonstrated broad activity against diverse dipeptides. The binding site for Cys-Gly-3M3SH was predicted using modelling, which suggested mutations that might accommodate this ligand more favourably. Indeed, a D437A resulted in an almost 6-fold increase in the kcat/KM, while other introduced mutations reduced or abolished function. Together these data identify an enzyme capable of catalysing the missing step in an ancient human-specific biochemical transformation and suggest that the production of 3M3SH neither uses a dedicated transporter nor peptidase for its breakdown, with only the final cleavage step, catalysed by PatB C-S β-lyase, being a unique enzyme.

Identification of a higher C-S lyase activity of Staphylococcus hominis in volunteers with unpleasant axillary odour.

Excessive and unpleasant odours that emanate from the skin can induce bromhidrosis and substantially impair a person's quality of life. Enzymatic pathways generating unpleasant odours are well detailed, and among them, the C-S lyase is one of the enzymes involved in the conversion of non-volatile precursors into thiol-type malodorous volatile molecules such as 3M3SH. This study aimed to investigate the variation of axillary odour intensity correlated with Staphylococcus (S.) hominis C-S lyase activity within a group of volunteers after a physical activity. First, a group of 24 volunteers from the same ethnicity with standardized hygienic and alimentary practices participated in a supervised indoor cycling activity. Following this session, worn T-shirts were recovered to enable the olfactory evaluation of axillary odours by qualified experts. To go further, the microbiota from the axillary zone of each volunteer was sampled and the bacterial relative abundance was investigated by using 16S rRNA metasequencing. Then, S. hominis isolates were obtained by culturomics from these microbiota samples and the C-S lyase activity was measured by spectrofluorometry in protein crude extracts. The evaluation of the odour intensity revealed that within the panel, two groups were significantly distinct. A non-odorous group and a malodorous one with volunteers having unpleasant odours. The 16S rRNA metasequencing reveals differences in bacterial communities between the two groups with a significant increase in the relative abundance of S. hominis in the malodorous group compared with the non-odorous one. The C-S lyase activities measured on S. hominis sampled on volunteers from the two groups demonstrate that for an equivalent quantity of protein, this enzymatic activity is significantly higher for the samples originating from the malodorous group. Hence, this study demonstrates that beyond the increase of S. hominis relative abundance, the C-S lyase enzymatic activity of this bacteria is also higher in volunteers with unpleasant axillary odours.

Blunt dissection of the axillary flap through double mini-incisions on both sides of the axilla to prevent postoperative hematoma.

The purpose of this study was to investigate the clinical effect of treating axillary osmidrosis by trimming the apocrine glands under direct vision after blunt dissection of the axillary flap through double mini-incisions on both sides of the axilla to prevent postoperative hematoma. The clinical data of 108 patients with axillary osmidrosis were retrospectively analyzed. Treatment involved blunt dissection of the axillary flap through double mini-incisions and trimming of the apocrine glands under direct vision. The surgical duration, hematoma incidence, flap necrosis rate, incision healing rate, incision VSS score, comfort level, axillary odor cure rate, and satisfaction rating were all statistically analyzed. The average surgical duration was 72.45±5.71 min. The cure rate of axillary osmidrosis was 100%. Postoperative complications, including delayed incision healing 12 days after surgery (1 patient), a small hematoma (2 patients), and local flap necrosis (1 patient), were minor. No infection, malodor, or recurrence was observed. The VAS score for patient comfort was 8.53±0.89, the VAS score for patient satisfaction was 8.87±0.98, and the VSS score for the incision was 0.84±0.99. This retrospective study demonstrated that the trimming of apocrine glands after blunt dissection of the axillary flap through double mini-incisions on both sides of the axilla effectively controlled bleeding. This approach significantly reduces the complication rate of axillary osmidrosis surgery and ensures the complete trimming of apocrine glands, eradicating axillary odor and maintaining a good appearance.

Identification of Microbiota Causing Bromhidrosis in the Axillary

Bromhidrosis is a clinical condition defined by an uncomfortable or unpleasant body odor. Since the apocrine glands are only active during puberty, most bromhidrosis occurs in the apocrine glands in the armpit and occurs when apocrine gland secretions approach the skin's surface, where they undergo various biochemical reactions caused by the presence of microbiota in the axillary skin, resulting in odor in the axilla. This research aims to identify microbiota species in the axilla that can cause bromhidrosis. A laboratory experimental research design with purposive sampling is used in this study. In this study, 60 samples were collected from students aged 15 to 18 years old at a high school in Medan, and the samples were analyzed at the University of North Sumatra Hospital's Microbiology Laboratory. All samples were taken from the right axillary skin swab, a Gram stain was performed, and the identified microbiota isolates were identified. The results of skin smear culture revealed a Gram-positive cocci group in 59 samples (98.3%) and a Gram-positive bacilli group in only one sample (1.7%). The microbiota responsible for bromhidrosis was identified as Staphylococcus hominis spp. hominins (30.4%), Staphylococcus epidermidis (27.8%), Staphylococcus aureus (16.5%), Kocuria kristinae and Staphylococcus haemolyticus (6.3%), Staphylococcus lugdunensis and Staphylococcus saprophyticus. The most common microbiota that causes bromhidrosis in the axilla is Staphylococcis hominis spp. Hominis, Staphylococcus epidermidis, and Staphylococcus aureus.

Olfactory facilitation of visual categorization in the 4-month-old brain depends on visual demand.

To navigate their environment, infants rely on intersensory facilitation when unisensory perceptual demand is high, a principle known as inverse effectiveness. Given that this principle was mainly documented in the context of audiovisual stimulations, here we aim to determine whether it applies to olfactory-to-visual facilitation. We build on previous evidence that the mother's body odor facilitates face categorization in the 4-month-old brain, and investigate whether this effect depends on visual demand. Scalp electroencephalogram (EEG) was recorded in two groups of 4-month-old infants while they watched 6-Hz streams of visual stimuli with faces displayed every 6th stimulus to tag a face-selective response at 1Hz. We used variable natural stimuli in one group (Nat Group), while stimuli were simplified in the other group (Simp Group) to reduce perceptual categorization demand. During visual stimulation, infants were alternatively exposed to their mother's versus a baseline odor. For both groups, we found an occipito-temporal face-selective response, but with a larger amplitude for the simplified stimuli, reflecting less demanding visual categorization. Importantly, the mother's body odor enhances the response to natural, but not to simplified, face stimuli, indicating that maternal odor improves face categorization when it is most demanding for the 4-month-old brain. Overall, this study demonstrates that the inverse effectiveness of intersensory facilitation applies to the sense of smell during early perceptual development. RESEARCH HIGHLIGHTS: Intersensory facilitation is a function of unisensory perceptual demand in infants (inverse effectiveness). This inverse relation between multisensory and unisensory perception has been mainly documented using audiovisual stimulations. Here we show that olfactory-to-visual facilitation depends on visual demand in 4-month-old infants. The inverse effectiveness of intersensory facilitation during early perceptual development applies to the sense of smell.

Emotion perception through the nose: how olfactory emotional cues modulate the perception of neutral facial expressions in affective disorders

Humans can decode emotional states from the body odors of the conspecifics and this type of emotional communication is particularly relevant in conditions in which social interactions are impaired, as in depression and social anxiety. The present study aimed to explore how body odors collected in happiness and fearful conditions modulate the subjective ratings, the psychophysiological response and the neural processing of neutral faces in individuals with depressive symptoms, social anxiety symptoms, and healthy controls (N = 22 per group). To this aim, electrocardiogram (ECG) and HD-EEG were recorded continuously. Heart Rate Variability (HRV) was extracted from the ECG as a measure of vagal tone, event-related potentials (ERPs) and event-related spectral perturbations (ERPSs) were extracted from the EEG. The results revealed that the HRV increased during the fear and happiness body odors conditions compared to clean air, but no group differences emerged. For ERPs data, repeated measure ANOVA did not show any significant effects. However, the ERPSs analyses revealed a late increase in delta power and a reduced beta power both at an early and a late stage of stimulus processing in response to the neutral faces presented with the emotional body odors, regardless of the presence of depressive or social anxiety symptoms. The current research offers new insights, demonstrating that emotional chemosignals serve as potent environmental cues. This represents a substantial advancement in comprehending the impact of emotional chemosignals in both individuals with and without affective disorders.

Patient and quality characteristics in the treatment with disulfiram (Antabus) in the German "Network for Alcohol Aversive Pharmacotherapy"

More than adecade ago disulfiram lost its approval for use in Germany. Nonetheless, aconsiderable number of psychiatric hospital outpatient departments as well as practicing physicians continue to prescribe it. These professionals have formed the "Network for Alcohol Aversive Pharmacotherapy" (NAP) to maintain a high quality of this treatment approach. To describe the current use of disulfiram with respect to patient numbers and characteristics, side effects, and use of concomitant multimodal treatment forms. Since 2019 the NAP has conducted an annual retrospective survey among its members regarding the aforementioned parameters. From 2019 to 2023 atotal of 1579 treatment cases were described by 33centers, 152 patients reported atotal of 241 drinking events, 26of them resulting in hospitalization but none causing complications or permanent harm. The most frequent side effects, in descending order, were unpleasant body odor (2.5%), fatigue, male sexual dysfunction, mildly elevated liver enzymes, allergic skin reactions and polyneuropathy (0.8%). More than one quarter of the patients suffered from comorbid depression, and approximately 5% from ADHD, borderline or other personality disorders, trauma-related disorders and anxiety disorders, respectively. Of the patients 33% were treated with antidepressants and 12% with sedating antipsychotics. Various forms of concomitant group therapy were offered to 66% of the patients. Treatment with disulfiram is legally possible, generally well-tolerated and safe. It is offered in most treatment centers as part of acomprehensive treatment plan that includes multimodal treatment of comorbid psychiatric disorders.

The Context Matters: Women's Experiences of Their Partner's Odor in Intimate and Sexual Encounters.

Research shows that male body odor plays an important role in women's mate choice and that olfactory abilities are associated with women's sexual functioning. What remains unclear is what types of partner's odor actually shape women's experience during intimate activities. This study therefore explored women's experience associated with the partner's various odors and investigated how they affect women's intimate and sexual encounters. We performed semi-structured individual interviews with 20 single women and 20 women in a long-term relationship. Thematic analysis revealed four key natural odor types of the partner: body odor, sweat, genital odor, and semen odor. Further, we have identified three main types of fragrance odor (cologne, shower gel, and laundry agents) and investigated their perception in both intimate (hugging, kissing, cuddling, lying side by side) and sexual (intercourse, oral sex, ejaculation) contexts. Both partner's natural odor and fragrance affected women's emotional state (ranging from pleasant to unpleasant) and behavioral response (ranging from approach to avoidance of partner). Women's odor perception was frequently context-dependent, so that even mostly negatively perceived odors (e.g., semen, genital odor) were often accepted as part of sexual encounter. Finally, women's perception was negatively modified by partner's specific sweat (after workday, workout, or when the partner is ill) during intimate encounters. Our results highlight the complexity and interindividual variability of partner's odor perception.

Analytical characterization of volatiles present in the whole body odour of zebra finches

In recent decades, the compositions of preen oil and feathers have been studied to achieve insights into the chemistry of avian odours, which play a significant role in birds’ social behaviour. Fewer studies are available regarding volatiles originating from other sources, such as faeces, eggs or a bird’s whole body. The aims of this study were (i) to identify odour-active and further volatile compounds in zebra finch whole body odour and (ii) to semi-quantify selected volatiles and use the information to evaluate two different adsorbents for their suitability for whole body odour sampling. Volatiles from the headspace above zebra finches were sampled using an open loop system equipped with either activated charcoal or Tenax® TA. Samples were analysed by olfactory-guided approaches as well as gas chromatography–mass spectrometry. Using activated charcoal as sorbent, 26 odour-active and 73 further volatile compounds were detected, whereas with Tenax® TA 27 odour-active and 81 further volatile compounds were detected. In total, 104 compounds were (tentatively) identified, of which 22 had not been identified previously in zebra finch odour and 12 had not been described in any birds. Hints towards a chemical sex signature became evident for qualitative but not for quantitative differences. With the exception of some compounds, notably carboxylic acids and alkanes, relative peak areas obtained with the two adsorbent types were comparable. The approach described herein is proposed for future studies aiming to determine volatiles emitted by birds when, for example, parent birds are approaching the nest.Graphical

Human perception of Parkinson's disease body odor in comparison to the volatile organic compounds of Parkinson's disease

IntroductionPatients with Parkinson's Disease (PD) have a distinctive body odor, which was first described by a patient's wife as musky and strong. Later analysis of sebum of patients with PD revealed four volatile organic compounds (VOC) (perillic aldehyde, hippuric acid, eicosane, octadecanal), that differed from healthy subjects, and the patient's wife confirmed that three of them smelled like patients with PD. However, it is unclear whether other people can also perceive this PD body odor and whether it can be artificially recreated. Hence, we aimed to systematically assess whether young women can perceive the PD body odor and whether they can discriminate between the PD body odor and the “artificial PD odor” composed of the four VOCs mentioned above. MethodsT-shirts were collected from 19 people with idiopathic PD and 15 age- and gender-matched healthy participants to represent the PD body odor and the healthy body odor, respectively. The four VOCs were diluted in 1,2-propanediol to prepare the artificial PD body odor. Body odors were rated by 26 young women. ResultsPD body odor was perceived as more musty, strong, smelly, and unpleasant compared to healthy and artificial PD body odor. Furthermore, around 80 % of women were able to discriminate PD body odor from artificial PD body odor. ConclusionOverall, this study confirmed a distinctive body odor quality of patients with PD, which can be perceived by young women. However, the four VOCs, composing the artificial PD body odor, were insufficient to reproduce the body odor from PD patients.

Combined perceptual and chemical analyses show no compelling evidence for ovulatory cycle shifts in women's axillary odour.

Although men's attraction to women's body odour has been suggested to vary over the ovulatory cycle, peaking around the fertile window, we still lack methodologically robust evidence corroborating this effect. Further, the chemical underpinnings of male preference for the odour of ovulating women remain unknown. Here, we combined perceptual and chemical analyses to investigate the axillary odour of naturally cycling women over 10 days, covering the gradual change in fertility across the ovulatory cycle with a focus on fertile days. The fertile state was confirmed by urinary ovulation tests as well as salivary oestradiol and progesterone levels. Men rated the scent of unfamiliar women, resembling a first encounter. We used multivariate analyses to relate variation in both odour ratings and chemical composition to female conception probability, temporal distance to ovulation and ovarian hormone levels. Our results provide no evidence that males prefer the odour of fertile women. Furthermore, the volatile analysis indicated no link between axillary odour composition and current fertility status. Together, our results showed no convincing support for a chemical fertility cue in women's axillary odour, questioning the presence of olfactory fertility information that is recognizable during first encounters in modern humans.

Do sheep (Ovis aries) discriminate human emotional odors?

While sheep can detect and discriminate human emotions through visual and vocal cues, their reaction to human body odors remains unknown. The present study aimed to determine whether sheep (Ovis aries) can detect human odors, olfactorily discriminate stressed from non-stressed individuals, and behave accordingly based on the emotional valence of the odors. Axillary secretions from 34 students were collected following an oral examination (stress odor) or a regular class (non-stress odor). Fourteen female and 15 male lambs were then exposed to these odors through a habituation-dishabituation procedure. The habituation stimulus was presented four times for one minute, followed by the dishabituation stimulus presented once for one minute. Behavioral variables included spatiality relative to target odors, approach/withdrawal, ear positioning, sniffing, ingestion, and vocalization. Both female and male lambs more often positioned their ears backwards/forwards, and asymmetrically when exposed to the dishabituation stimulus, but regardless of their stress or non-stress value. They also changed their approach behavior when exposed to the dishabituation stimuli. Lambs displayed some behavioral signs of discrimination between the habituation and dishabituation odors, but regardless of their relation to stress or non-stress of human donors. In sum, this exploratory study suggests that young sheep respond negatively to the odor of unfamiliar humans, without showing any specific emotional contagion related to the stress odor. This exploratory study suggests young ovines can detect human body odor, a further step toward understanding the human-sheep relationship.

Oxytocin induces the formation of distinctive cortical representations and cognitions biased toward familiar mice

Social recognition is essential for the formation of social structures. Many times, recognition comes with lesser exploration of familiar animals. This lesser exploration has led to the assumption that recognition may be a habituation memory. The underlying memory mechanisms and the thereby acquired cortical representations of familiar mice have remained largely unknown, however. Here, we introduce an approach directly examining the recognition process from volatile body odors among male mice. We show that volatile body odors emitted by mice are sufficient to identify individuals and that more salience is assigned to familiar mice. Familiarity is encoded by reinforced population responses in two olfactory cortex hubs and communicated to other brain regions. The underlying oxytocin-induced plasticity promotes the separation of the cortical representations of familiar from other mice. In summary, neuronal encoding of familiar animals is distinct and utilizes the cortical representational space more broadly, promoting storage of complex social relationships.

Olfactory-to-visual facilitation in the infant brain declines gradually from 4 to 12 months.

During infancy, intersensory facilitation declines gradually as unisensory perception develops. However, this trade-off was mainly investigated using audiovisual stimulations. Here, fifty 4- to 12-month-old infants (26 females, predominately White) were tested in 2017-2020 to determine whether the facilitating effect of their mother's body odor on neural face categorization, as previously observed at 4 months, decreases with age. In a baseline odor context, the results revealed a face-selective electroencephalographic response that increases and changes qualitatively between 4 and 12 months, marking improved face categorization. At the same time, the benefit of adding maternal odor fades with age (R2 = .31), indicating an inverse relation with the amplitude of the visual response, and generalizing to olfactory-visual interactions previous evidence from the audiovisual domain.