A person who has consumed a significant amount of alcohol emits a distinct odor, often called “alcohol breath.” While the smell can come through the pores, the skin is not the primary source. The majority of the scent comes from unmetabolized ethanol leaving the body through the breath. This pervasive smell occurs because the body can only process alcohol at a fixed rate, leading to the temporary circulation and expulsion of the compound through multiple routes.
How the Body Processes Alcohol
The body recognizes ethanol, the type of alcohol in beverages, as a foreign substance that must be neutralized or eliminated. The liver is the primary organ responsible for this detoxification process, handling over 90% of the alcohol consumed. This process is a two-step chemical transformation involving specialized enzymes.
The first step involves the enzyme alcohol dehydrogenase (ADH), located in the liver cells. ADH converts ethanol into a highly toxic compound known as acetaldehyde. This intermediate substance is responsible for many unpleasant physical effects associated with heavy drinking.
The second step quickly follows, where the enzyme aldehyde dehydrogenase (ALDH) converts acetaldehyde into acetate. Acetate is a much less harmful compound that the body breaks down into carbon dioxide and water, or uses for energy. The rate at which the liver completes this two-step breakdown is relatively constant, regardless of the amount of alcohol consumed.
Because the liver has a maximum processing capacity, consuming alcohol faster than it can neutralize it leads to a build-up. This excess, unmetabolized ethanol then circulates throughout the bloodstream and the body’s tissues. This saturation necessitates the body to use other pathways for elimination until the liver can catch up.
Excretion: Skin Versus Breath
The body primarily excretes small amounts of unmetabolized alcohol through three non-metabolic routes: the breath, the urine, and the skin. These routes collectively account for a small fraction, typically between 2% and 10%, of the total alcohol eliminated. The largest portion of this non-metabolic excretion is through the lungs.
As blood saturated with ethanol flows through the air sacs in the lungs, the volatile alcohol crosses the membrane and evaporates into the exhaled breath. This is the same principle used by a breathalyzer device to estimate blood alcohol concentration. The lungs are the dominant non-metabolic route, accounting for a significantly higher proportion of expelled alcohol than the skin.
While a small amount of ethanol is secreted through the skin’s eccrine sweat glands (pores), the total quantity is minute by comparison. Studies suggest the amount of alcohol excreted via sweat may be less than one-tenth of the amount expelled through the breath. The scent associated with “alcohol sweat” is often a combination of this trace amount of ethanol and other metabolic byproducts mixing with perspiration.
Why the Odor Lingers
The persistence of the alcohol smell is directly related to the time it takes for the liver to complete the metabolic process. The odor continues to be emitted as long as unmetabolized ethanol circulates in the bloodstream and is expelled through the lungs and skin. Since the liver processes alcohol at a fixed rate, the only way for the smell to completely disappear is to wait for this process to finish.
The compounds responsible for the lingering scent are primarily the unmetabolized ethanol being constantly exhaled. The odor is often made more pungent by the presence of the toxic intermediate, acetaldehyde. While the liver is efficient at converting acetaldehyde to acetate, some of it can also become volatile and be expelled via the breath and sweat. The smell ceases only when the concentration of both ethanol and its immediate byproduct falls to zero in the body.