My dad sweat smell so foul

Foul body odor (especially sweat) is quite common and usually has straightforward causes. Here are the main reasons:

Common Causes of Foul Sweat Smell:

Apocrine gland activity - These sweat glands (in armpits, groin) produce a thicker sweat that bacteria on the skin break down into smelly compounds. This is the main source of body odor.
Diet - Foods like garlic, onions, red meat, spicy foods, and alcohol can make sweat smell worse. These compounds are excreted through the skin.
Poor hygiene - Infrequent bathing or not changing clothes allows bacteria to build up.
Hyperhidrosis - Excessive sweating creates more substrate for bacteria to act on.
Medical conditions that can cause unusually foul odor:
- Diabetes - can cause a sweet or fruity/acetone smell
- Kidney disease - ammonia-like or fishy smell
- Liver disease - musty or bleach-like smell
- Trimethylaminuria (Fish Odor Syndrome) - a metabolic disorder causing a strong fishy smell
- Infections (skin, fungal) - localized foul smell
- Certain medications
Age-related changes - Older adults can develop "nonenal," a compound that produces a grassy/greasy odor sometimes called "old person smell."

What can help:

Shower daily, especially after sweating
Use antibacterial soap on odor-prone areas
Apply antiperspirant/deodorant
Wear breathable, natural fabrics (cotton, linen)
Stay hydrated and improve diet (reduce red meat, garlic, alcohol)
Change clothes frequently

When to see a doctor:

If the smell is sudden, very intense, or has a specific character (fishy, ammonia, fruity/sweet), it could signal an underlying medical condition that needs evaluation - particularly kidney disease, liver problems, or diabetes.

Is the smell a particular type (fishy, ammonia-like, sweet)? That can help narrow down if there's a specific cause to look into.

It started 2 month ago before he's good

A sudden change in body odor that started 2 months ago (when it was fine before) is more medically significant than long-standing odor. This points more toward an underlying cause rather than just hygiene.

Most likely reasons for a sudden onset:

🔴 Medical Causes to Rule Out First

These are the more serious ones that need a doctor visit:

Condition	Smell Type	Other Signs
Diabetes / High blood sugar	Sweet, fruity, or acetone	Increased thirst, frequent urination, fatigue, weight loss
Kidney disease	Ammonia or urine-like	Swelling in legs, fatigue, foamy urine
Liver disease	Musty, sweet-rotten	Yellowing of eyes/skin, fatigue, dark urine
Infection (skin, abscess, etc.)	Foul, localized	Redness, swelling, fever
Hyperthyroidism	More intense general odor	Weight loss, sweating more, feeling hot, rapid heart rate

🟡 Lifestyle Changes (2 months ago - did anything change?)

New medication started?
Diet change (more red meat, alcohol, processed food)?
Increased stress or illness?
Weight gain?

🟢 Less Serious but Common

New bacteria/fungal overgrowth on skin
Hormonal shift

The key question is: did anything else change 2 months ago? A new medication, a health event, dietary shift, or new symptom alongside the smell can point directly to the cause.

Given the sudden onset, a doctor visit is genuinely recommended - a basic blood test (blood sugar, kidney function, liver function) can rule out the most important causes quickly. It could be nothing serious, but it's worth checking.

He is not on any medication

That rules out medication as the cause, which actually makes a medical condition more likely to be behind the sudden change.

Since he's not on any medications, here's where to focus:

The Most Important Question: What does the smell actually like?

This matters a lot for figuring out the cause:

Sweet / fruity / like nail polish remover → Diabetes or pre-diabetes (very common, often undiagnosed)
Ammonia / urine-like → Kidney problems
Musty / slightly rotten-sweet → Liver issues
Fishy → Trimethylaminuria or kidney disease
Just very strong / pungent sweat → Infection, hyperthyroidism, or dietary cause

Other symptoms to watch for in your dad:

Is he more thirsty or urinating more than usual? (Diabetes)
Has he lost weight without trying? (Diabetes, thyroid, cancer)
Is he more tired than before? (Many conditions)
Does his skin look yellow or his eyes look yellow? (Liver)
Is he sweating more than before? (Thyroid, infection)
Any swelling in the legs or feet? (Kidney/heart)

Bottom Line

No medication + sudden onset 2 months ago = please take him to a doctor for a basic checkup. Ask for:

Fasting blood glucose (diabetes)
Kidney function (creatinine, urea)
Liver function tests
Thyroid function (TSH)

These are simple blood tests that can identify most of the serious causes quickly. Catching something like diabetes early makes a huge difference in treatment outcome.

How old is your dad, and have you noticed any of those other symptoms?

He sweat a lot before this also if he's at home he doesn't wear proper clothes he's only in towel

That's really helpful context. So he already had hyperhidrosis (excessive sweating) before - that's been his baseline. But the smell changed 2 months ago even though the sweating itself isn't new.

This is an important distinction - the sweating didn't change, just the odor did.

What this tells us:

The bacteria on his skin were already dealing with a lot of sweat before, but the odor was manageable. Something changed internally 2 months ago that altered what's being excreted through his sweat.

Top suspects given this picture:

Dietary change - Did he start eating differently? More red meat, fermented foods, garlic, onions, or alcohol?
Blood sugar / Diabetes - Very common, often develops gradually. The body starts excreting different compounds through sweat as blood sugar rises.
Hormonal change - Testosterone shifts, thyroid changes can alter sweat composition noticeably.
Gut health / microbiome change - A gut imbalance (dysbiosis) can cause compounds to be absorbed and excreted through sweat.
Skin bacteria change - The type of bacteria colonizing his skin may have shifted, producing different odor compounds from the same sweat.

Practical steps right now:

Hygiene adjustments:

Shower at least twice daily since he sweats heavily
Use antibacterial soap (like Dettol or Dial) especially on armpits, groin, chest
Dry completely after showering - bacteria thrive in moisture
Even at home, wearing a light cotton t-shirt helps absorb sweat and reduce bacterial buildup on skin
Apply antiperspirant (not just deodorant) after showering

Diet check:

Cut back on red meat, garlic, onions, spicy food for 2 weeks and see if it improves

But still - a doctor visit is the right move given it's a sudden change with no obvious trigger. A simple blood test will either catch something important or give you peace of mind.

How old is he roughly, if you don't mind?

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