Body odour

Body odour is the smell produced when bacteria on the skin break sweat down. Sweat itself barely smells.

First, why this slot was made separately.

The aluminium salts page already carried this sentence — 'an antiperspirant and a deodorant are different things. A deodorant deals with smell; an antiperspirant deals with sweat.'

The distinction is right, but there was nowhere for someone looking for smell to land. Send them to sweating and they read about volume. We separated it for the same reason as the bruising, leg veins and cellulite slots.

Why sweat and smell are different problems.

• sweat is mostly water. Eccrine sweat holds little of what makes a smell
• the smell comes from the apocrine side. Those glands sit in the armpits and a few other places, and the smell appears as bacteria break their secretions down
• so the bacteria are a variable. The same amount of sweat smells differently
• hair and clothing are variables too. They are where the smelling compounds stay

Reducing sweat ought to reduce smell — but that is something to be measured, not assumed.

Two things are filed here, and both aim at sweat.

• aluminium salts — the active in antiperspirants. The most striking thing on that page is what is absent: for a product this many people use daily, we found no trial against a placebo
• miraDry — a device that treats sweat glands with microwaves. It is described as being used for smell too, but what its trial took as an endpoint was sweat

So the content of this slot is not 'what works'. It is that nobody measured odour as an endpoint. There is not one trial on this site that puts a number on smell.

Why that gap exists can be guessed at. Deodorants are cosmetics or quasi-drugs in most countries. They are not asked for licensing trials the way a new drug is, and the effect has been known so long that there is little reason to run a fresh placebo-controlled trial. But 'no trial was required' and 'a trial was done' are different sentences.

Finally, when this may not be a cosmetic matter.

If your smell has suddenly changed, that is not a cosmetic signal. Diabetes, liver and kidney problems, infections, and rarely metabolic conditions in which a particular compound is not broken down all change how a person smells. A sudden change, a strong smell that returns after washing, or other symptoms alongside it mean seeing a clinician first. This site does not make that judgement for you.