The unsettling sensation known as “the spins” is a form of medically-defined vertigo caused by acute alcohol intoxication. This experience involves the false perception that you or your surroundings are in continuous, rapid motion, even when you are lying perfectly still. This intense disorientation often leads to nausea and vomiting, signaling a profound disruption in the body’s internal balancing mechanisms. The phenomenon is a direct result of alcohol infiltrating and temporarily altering the delicate mechanics of the inner ear.
The Body’s Balance Center
The body’s ability to maintain equilibrium and spatial awareness is managed by the vestibular system, a complex sensory apparatus housed deep within the inner ear. This system includes three tiny, fluid-filled tubes called the semicircular canals, which are oriented at right angles to one another, allowing them to detect rotation in all three dimensions of space. Each canal contains a fluid called endolymph, which moves in response to head rotation.
Bridging the canal is a small, gelatinous, dome-shaped structure called the cupula. Embedded within the cupula are tiny, hair-like sensory cells, known as stereocilia. When the head moves, the endolymph lags behind due to inertia, pushing against the cupula and bending the stereocilia. This mechanical bending generates electrical signals that travel to the brain, informing it of the speed and direction of the head’s rotation. Under normal conditions, the cupula and the surrounding endolymph have the same density, making the cupula naturally insensitive to gravity.
Alcohol’s Effect on Inner Ear Fluid Density
The core mechanism behind the spins begins once alcohol is absorbed into the bloodstream and reaches the inner ear. Alcohol is less dense than the water that makes up the body’s fluids, and this density difference disrupts the vestibular system.
Alcohol rapidly diffuses from the blood into the water-based endolymph fluid within the semicircular canals. However, it diffuses into the gelatinous cupula tissue at a slightly slower rate. This difference in diffusion rates causes the endolymph to become slightly less dense than the cupula for a temporary period. This creates a buoyancy difference where the cupula is effectively heavier than the surrounding fluid, causing it to sink or drift unnaturally.
This density difference turns the cupula into a gravity-sensitive float, a state known as positional alcohol nystagmus (PAN). The cupula’s displacement bends the sensory hair cells. This unnatural bending sends a constant, false signal to the brain, which incorrectly registers the sensation as continuous rotational movement. The time during which the alcohol concentration is higher in the cupula than the endolymph is referred to as PAN I, and it is the primary phase responsible for the most intense spinning sensation.
The Illusion of Movement (Vertigo)
The brain’s interpretation of this false signal results in the intense sensation of vertigo. Since the cupula is being unnaturally distorted, the stereocilia send a continuous stream of impulses that mimic the feeling of accelerating rotation. The brain receives this vestibular information, which insists the body is spinning, but it cannot reconcile it with the visual information from the eyes, which shows a stationary room.
This sensory conflict leads to profound disorientation and the perception that the environment itself is moving. When the eyes are closed, the brain loses the only reliable sensory input it has—vision—to counteract the false vestibular signal. This lack of visual anchoring allows the misfiring balance system to dominate the perception of reality, which is why closing your eyes often intensifies the feeling of spinning out of control. The brain’s attempt to make sense of the conflicting signals frequently triggers the body’s motion sickness response, leading to severe nausea and vomiting.
The Dual Effect and Recalibration
The spinning sensation often intensifies dramatically when a person lies down because of the gravity-sensitive nature of the compromised system. When the head is tilted or lying down, the cupula’s abnormal buoyancy allows gravity to exert maximum influence. This change in head position reorients the canals, allowing the density imbalance to cause a greater, gravity-driven displacement of the cupula, thereby increasing the false signal.
The spinning sensation only begins to resolve once the alcohol concentrations in the inner ear fluid and the cupula begin to re-equilibrate. As alcohol is metabolized and leaves the bloodstream, it diffuses out of the cupula first, which can temporarily cause the cupula to become denser than the surrounding endolymph fluid. This creates a second, less intense phase of positional alcohol nystagmus (PAN II), which often results in a final, brief period of spinning in the opposite direction. Ultimately, the sensation disappears completely only when the densities of the cupula and endolymph return to their normal, equalized state.