Introduction

Humans generate an array of odours, not all of which are nice like stinky feet and smelly armpits. Body odour is quite a normal issue as it affects you and everyone you know at some point in their lives. The odours are usually caused by bacteria, especially bacteria that are found in your skin and react with specific chemicals while you are sweating to produce the bad smells. Deodorants and antiperspirants can help to hide body odours, however the odour might also indicate an underlying ailment.¹

When it comes to body odour, the saying "you are what you eat" is particularly applicable. Your body reacts to what you eat and drink which causes the bad odour. Most individuals and you might not notice that this is normal.²

What causes body odour?

Apocrine, eccrine, and sebaceous are the three types of sweat glands found in humans. The eccrine sweat glands are present in the entire skin while apocrine and sebaceous are present in particular regions. Furthermore, while going through puberty the apocrine sweat glands are stimulated which leads to body odour. Hairy regions, such as armpits, the scalp, and genitals, are where sweat glands release oily liquids that contain protein, lipids, and steroids. Despite sweat being odourless, body odour happens when microorganisms mix with the sweat causing the formation of malodorous by-products. The armpits in humans are the best place for microbes to habitat as it is moist and warm.¹

Biochemistry of body odour

The anatomy of the skin microbiota varies from person to person and between regions on the same host. For instance, the left armpit can have a significantly different flora than the right. Nonetheless, there are similarities among the main bacterial species that invade the skin and produce body smell. Corynebacterium, Staphylococcus, and Cutibacterium are the skin bacteria that cause body odour.¹

The biochemistry of microbial sweat conversion to malodorous compounds is still not fully understood. Volatile organic compounds (VOCs), like volatile fatty acids and thioalcohols, are believed to cause the body odour. 3-methyl-2-hexenoic acid (3M2H) is a important volatile fatty acid that causes the body odour to smellgoat-like. The cumin-like smell is caused by 3-hydroxy-3-methylhexanoic acid (HMHA). These odours are produced by the bacterial species Corynebacterium striatum, Corynebacterium jeikeium, and Corynebacterium bovis.

Body odour is caused by the short-chain fatty acids and various intermediates. Staphylococcus epidermis present in the skin changes the leucine in the sweat into isovaleric acid (cheesy-smelling compound). Thioalcohols derive their foul odour from sulphur and, despite being present in small amounts, are among the most potent VOCs generated. Staphylococcus hominis produces thioalcohol (3-methyl-3-sulfanylhexan-1-ol) that makes the odour resemble meat or rotten onion in the armpits. S. hominis encodes a proton-coupled oligopeptide transporter that brings the thioalcohol-conjugated precursor S-Cys-Gly-3M3SH into the cell, where it is catabolised to produce the foul-smelling 3M3SH.¹

Other factors that cause body odour

Diet, hormones, and medication are various factors that impact the body and its odours. A person who sweats too much has a disorder known as hyperhidrosis. Individuals with these disorders sweat excessively which causes them to have body odour. This is also uncomfortable due to sweaty feet and palms.³

The foul body odour is developed when you sweat. Noticeable body odours are more common in certain individuals than in others.

Factors that can affect body odour include:³

• Stress or worry
• Hot weather
• Being overweight/obese
• Genetics
• Exercise

Unpleasant body odour is caused by particular medicine, foods, and supplements. Remember that the scent comes from the microorganisms on your skin, not the sweat itself.

Individuals’ body odour changes are related to various medical conditions and diseases:³

• Diabetes
• Gout
• Menopause
• Overactive thyroid
• Liver disease
• Kidney disease
• Infectious diseases

Foods and drinks that affect the body odour

Individuals get body odour by consuming sulphur-rich meals. Sulphur smells like rotten eggs, soo when you sweat you smell bad. This is why the phrase "you are what you eat" can be used for your body odour. 

Cruciferous vegetables

The most noticeable cruciferous vegetables are kale, cabbage, cauliflower, and broccoli. They have a high amount of fibre that cannot be digested and once the fibre enters the colon it reacts with bacteria present and forms gas which you release. These vegetables have different amounts of sulphur-containing compounds which break down into hydrogen sulphide and smells like rotten eggs.²

Seafood

There is a metabolic condition individuals may encounter  when they eat seafood. This condition occurs when the body cannot break down the chemical trimethylaminuria present in seafood and individuals produce a fishy odour while eating them. The odour will appear within a few hours of consumption. It is diagnosed with a urine test. People with this disease may need to avoid shellfish and other foods containing trimethylamine precursors, such as eggs, liver, beans, and grass-fed cow's milk.² 

Spices

Curry, cumin, and fenugreek are strong spices that can stick to your tongue and teeth. These spices can stay on your breath for hours and stick to your hair, skin, and clothing. The volatile chemicals present in spices are absorbed in the bloodstream and released via sweat glands, giving unique odours.⁴

Asparagus

Consuming asparagus leads to your urine smelling like  rotten cabbage.This is due to sulphur compounds present in asparagus. However, not everyone produces an unpleasant odour when peeing, known as anosmia. There is a hypothesis that an enzyme is responsible for the creation of sulphurous metabolites that vary genetically. Anosmia is hypothesised to be caused by genetic diversity in one's olfactory genes. The good news is that there is no clinical concern if you have, don't have, or smell the odorous urine.²

Methods to eliminate body odour

Body odour can impact a person's daily life by making them feel unpleasant and disturbed by the smell. The best approach if you notice body odour quite frequently is to reconsider your eating habits and hygiene.

Personal hygiene and lifestyle

The following practices can help reduce body odour:⁴

• When showering or bathing use an antibacterial soap. Focus on your armpits, groin, and other areas where you frequently sweat. This will help you eliminate the bacteria on your skin and get rid of the odour.
• Hair is considered a haven for bacteria so shaving your armpits helps sweat to evaporate quickly and have less chance to mix with the bacteria in the skin.
• Your clothes should be washed often so that they are clean.
• Put on cotton clothes that fit loosely because there will be airflow for the skin. Bras and undergarments fall under this guideline as well. Clothing made of moisture-wicking material, which can draw moisture away from the skin, is also beneficial.
• Apply a topical antiperspirant. functions by attracting perspiration back into the sweat glands. Your body sends a signal that your sweat glands are full, which causes your sweat output to diminish. 
• Consider cutting out particularly odorous foods from your diet or observe whether certain foods exacerbate body odour. 
• Look for strategies to lessen your stress. Your apocrine glands may become active when you are stressed.

Natural methods

There are also effective solutions available if you choose a more natural method of reducing body odour under the arms. Consult a doctor about it but these might include:⁴

• Baking soda: Mix water and baking soda to form a paste. Put the paste under your arms, then allow it to dry. Baking soda lessens smells and regulates the acidity of your skin.
• Green tea: immerse green tea bags in warm water. Every day, for a few minutes, place the moistened tea bags beneath your armpits. Green tea could aid in pore blockage and decrease perspiration.
• Apple cider vinegar: In a spray bottle, combine apple cider vinegar and a tiny bit of water. Apply the concoction under your arms. Vinegar acid aids in the destruction of microbes.
• Lemon juice: In a spray bottle, combine lemon juice and water. Mist the blend beneath your arms. Bacteria are killed by the citric acid in lemon juice.

Summary 

Everyone has body odour and that is because bacteria available in the skin break down the sweat. The apocrine sweat glands are responsible for the production of sweat. Factors that influence body odour are diet, medications, health conditions, and genetics. Body odour can get worse if you consume seafood, spices, onion, garlic, and cruciferous vegetables due to them being sulphur-rich. Managing body odour requires personal hygiene, dietary adjustments, and natural remedies.