Bromhidrosis, sweating, and the link between the skin microbiome and gut microbiome

Why sweating is beneficial

• Regulates body temperature — cools you down during heat or physical effort

• Shows that the body responds normally to heat, exercise, and stress

• Indirectly supports skin function by maintaining thermal balance

What sweating does NOT do

• It does not significantly eliminate toxins (the liver and kidneys are responsible for detoxification)

• It does not automatically mean you burned more calories

When sweating may be a problem

• Excessive sweating without effort

• Night sweats

• Sweating with palpitations, dizziness, or weakness

• Very strong odor or sudden changes in body odor

Why sweat smells

Fresh sweat is mostly odorless. The smell appears when bacteria on the skin break down components of sweat and sebum.

Key areas:

• Armpits

• Feet

• Groin

Common microorganisms involved:

• Corynebacterium — often linked to strong underarm odor

• Staphylococcus — contributes to different odor profiles

• Fungi/yeasts — especially on the feet

This is why two people can sweat the same amount but smell completely different.

1. The microbiome–sweat connection

The skin microbiome = all bacteria, fungi, and microorganisms living on the skin.

Sweat changes the skin environment:

• moisture

• salt concentration

• pH

• temperature

These changes select for certain microbes — some produce more odor than others.

2. When odor may signal disease

Changes in body odor can sometimes be associated with:

• Diabetes → fruity smell (ketoacidosis = emergency)

• Chronic kidney disease → ammonia-like odor

• Liver disease → characteristic body odor changes

• Hyperthyroidism → increased sweating

• Obesity → more sweating + altered skin folds microbiome

• Skin or fungal infections

Important:Diseases usually don’t directly “create smell” — they change:

• how much you sweat

• sweat composition

• skin pH

• microbiome balance

• inflammation

3. What is hyperhidrosis?

Hyperhidrosis = excessive sweating beyond what’s needed for temperature regulation.

Types:

Primary (focal):

• palms

• soles

• armpits

• face

Secondary:

• thyroid disorders

• diabetes

• anxiety

• menopause

• infections

• medications

4. Hyperhidrosis and the microbiome

More sweat creates an environment that is:

• warmer

• wetter

• less ventilated

This favors:

• odor-producing bacteria

• fungi

Results:

• stronger odor

• irritation

• skin maceration

• fungal infections (especially feet)

• bromhidrosis

Often, the real issue is not just sweating — but how it reshapes the skin ecosystem.

5. What is bromhidrosis?

Bromhidrosis = persistent or excessive unpleasant body odor related to sweat + skin bacteria.

It can occur with:

• normal sweating + strong odor

• excessive sweating + strong odor

• heavy sweating without odor

Common types:

• Axillary (armpits) — most common

• Plantar (feet) — sweat + closed shoes + microbes

• Generalized — rarer, may need medical evaluation

6. How bromhidrosis develops

Odor comes from volatile compounds produced when bacteria break down:

• sweat

• sebum

• keratin

• skin debris

Contributing factors:

• hyperhidrosis

• synthetic clothing

• stress

• hormonal changes

• obesity

• diet

• altered skin microbiome

7. The gut–skin–sweat connection

This is where things get especially interesting.

A. The gut influences the skin indirectly

The gut microbiome affects:

• systemic inflammation

• metabolism

• immune function

• hormones

• stress response

• metabolic byproducts

This can influence:

• sweating amount

• sweat composition

• sebum production

• skin pH

• skin microbiome

This relationship is known as the gut–skin axis.

B. Practical examples

• Gut dysbiosis → may worsen:

  • acne

  • dermatitis

  • rosacea

  • possibly body odor in some individuals

• Diet high in sugar/ultra-processed foods:

  • affects insulin

  • increases inflammation

  • alters sweat and sebum composition

• Poor digestion / constipation:

  • doesn’t mean “toxins leave through sweat,”

  • but metabolism and volatile compounds can change

C. Can the gut directly change body odor?

Sometimes, yes.

Examples:

• Trimethylaminuria — fish-like odor

• Small intestinal bacterial overgrowth — may alter metabolic byproducts (odor link varies)

8. The key idea (put simply)

This is a bidirectional system:

• Gut → metabolism, hormones → sweat & skin environment

• Sweat → skin conditions → microbiome → odor

So bromhidrosis is not just about sweat — it’s about the interaction between sweat, microbes, and internal physiology.