THE RELATIONSHIP BETWEEN BODY ODOUR, THE AXILLA MICROBIOME AND PERSONAL HYGIENE.

Have you had any interaction with someone with body odour? How did you feel? Only recently, a group of student approached me and immediately I felt uncomfortable as I perceived that irritating smell. Although initially, I could not identify who amongst them had that malodour, immediately she moved a little closer, I had no choice but to educate her a little about the relationship between body odour, the axilla microbiome, and personal hygiene.
The anatomy and physiology of the skin vary from one part of the body to another, and the normal microflora reflects the variations. The epidermis has a slightly acidic pH, a high concentration of sodium chloride, a lack of moisture in many areas and the oily lubricant sebum and antimicrobial peptides in other areas.

The skin surface can be divided into three environmental niches: dry, moist and sebaceous. In general, bacterial diversity is greatest at dry sites (forearm, buttocks, hands) a mixed representation of Gram-positive and Gram-negative organisms from the phyla Actinobacteria, Bacteroidetes, Firmicutes and proteobacteria resides in these areas. Moist areas (umbilicus, underarm, inside the elbow, gluteal creases) exhibit less diversity, supporting mostly members of Firmicutes and Actinobacteria (Staphylococcus and Corynebacterium sp). The skin surfaces with the lowest bacterial diversity are the oily sebaceous sites where members of Actinobacteria are prevalent. Most skin bacteria are found on superficial cells, colonizing dead cells, or closely associated with the oil and sweat glands. Secretions from these glands provide the water, amino acids, urea, electrolytes and specific fatty acids that serve as nutrients primarily for resident bacteria such as S. epidermidis. Complex lipids secreted by oil glands are partially degraded by the enzymes from certain Gram-positive bacteria, particularly Propionibacterium acne.

These bacteria are usually harmless and are associated with acne vulgaris. They convert lipids secreted by the oil glands to unsaturated fatty acids such as oleic acid that have strong antimicrobial activity against Gram-negative bacteria and some fungi. Some of these fatty acids are volatile and may have a strong odour. Due to this reason, many deodorants contain antibacterial substances that act selectively against Gram-positive bacteria to reduce the production of volatile unsaturated fatty acids and body odour.

Sweating is a natural phenomenon which is essential for the regulation of body temperature. In the daily activities of all living beings, metabolic activities take place irresistibly all other things being equal. The hypothalamus acts by increasing the peripheral vasodilation and sweating to release heat. The eccrine glands are involved in thermoregulation and are found all over the body.

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What are the causes of sweating?

Sweating is a very common feature which can occur through any of the following conditions

Anxiety
Exercise
Consuming spicy foods, drugs (paracetamol, insulin, morphine, aspirin),
Intense concentration and increased sensitivity to circulating adrenaline

The gland of interest are the apocrine glands (sweat ducts) in the axilla which secrete nearly ten times as much sweat as the eccrine glands.These glands are found in the breasts, genital area, eyelids, armpits, and ear. Apocrine glands in the skin and the eyelids are sweat glands and they are located in several areas including the armpit. They are largest in the axilla where secretion of fluids is abundant and are responsible for the production of body odour.

What then is body odour?

Body odour occurs when the body gives off an odour or smell that others may find unpleasant or offensive; and this phenomenon usually becomes obvious when good personal hygiene is not observed before reaching puberty. Sweating excessively is a perquisite to body odour. Although sweat is odourless to humans, the rapid multiplication of bacteria in the presence of sweat and their breaking down of sweat into acids is what eventually causes the unpleasant smell. However, often the salt level of sweat is too high for the bacteria to break down to produce this unpleasant odour. It also depends on where the excess sweating is occurring and which type of sweat glands is involved.
Body odor as a result of sweat is most likely to occur in the armpit, genitals. Feet, groin, and the rest of the skin to a lesser extent.

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Who are those predisposed to body odour?

People who are obese
Those who regularly eat spicy food and drink – such as garlic, spices and alcohol
Men are also more susceptible to this condition as it is generally believe that men sweat more than the women.
People who sweat too much, such as those with hyperhidrosis (a condition where the sweat produced by a person is much more than what the body needs to regulate its temperature). Individuals with this condition may also have bromodosis also known as smelly feet which can be caused by wearing socks and shoes that prevents the sweat produced from evaporating and also from being absorbed and this attracts bacteria.
Individuals on some types of medication, such as antidepressants
People with certain medical conditions, for example a bleach-like smell may indicate liver or kidney disease while a fruity smell can sometimes is an indication of diabetes.

Prevention

The large concentration of apocrine glands that is present in the armpits makes it more susceptible to the rapid development of body odour through microbial activities and several steps can be taken to prevent this odour.
The population of axilla microbiome can be reduced or increased by the use of deodorants and antiperspirant that non selectively kills bacteria and veils the odour respectively.

Antiperspirants contain aluminium salts that blocks sweat production. Antiperspirant usage leads to increase of Actinobacteria which aids body odour development and increased diversity of bacteria(. In other words antiperspirant modify the microbial community and stimulate odour producing bacteria.

It is conventional that armpit hair enhances sweating in the axilla and gives a wide surface area and is effective with malodour.The function of the hair in the axilla, whether short or long still produced the same concentration of axilla malodour. Axillal hair acts as a collecting site for apocrine sweat and debris, makes cleansing of the area more difficult, thereby aiding malodour production. Ii will therefore advised that the armpit be kept clean

By washing and scrubbing it regularly with the use of antibacterial agent resulting in a decrease of bacterial population.
The shaving of the armpit regularly helps control body odour as the hair in the armpit slows down evaporation of sweat.
Through the use of deodorants that makes the skin more acidic, therefore making it more difficult for bacteria to survive.
In cases where severe body odour can't be treated by self-care measures as listed above, I will advise that the individual visit a general medical practitioner where surgery may be recommended.

In conclusion, good personal hygiene helps prevent body odour even in the presence of the axilla microbiome and vice versa.