When a strand of hair is accidentally swallowed, the body treats it like any other foreign material. Hair is composed almost entirely of keratin, a durable structural protein also found in fingernails and the outer layer of skin. While the thought of ingesting hair may cause concern, a small, isolated incident is generally harmless and common. A single hair typically navigates the gastrointestinal tract without issue.
The Digestive Journey: Why Hair is Indigestible
Hair does not dissolve in the stomach because the human body lacks the specific enzymes necessary to break down keratin. Standard digestive enzymes, such as pepsin, are unable to cleave the strong chemical bonds within the keratin structure. Hair is resistant to both the stomach’s strong hydrochloric acid and standard enzymatic activity.
Instead of being digested, the hair is moved through the digestive tract by peristalsis, the coordinated muscular contractions of the stomach and intestines. This wave-like motion pushes the indigestible strand along with other food matter and waste. A single, smooth piece of hair typically passes completely through the stomach and intestines over a few days.
The hair eventually exits the body naturally in the stool, unchanged from its original form. This passage is normally asymptomatic, meaning the individual experiences no discomfort or awareness of the hair’s movement. The smooth, slippery texture of hair allows it to travel easily through the gastrointestinal tract.
The Risk of Accumulation: Understanding Hairballs
While accidental ingestion of a few hairs is benign, the repeated swallowing of hair can lead to a rare but severe condition called a trichobezoar, or a hairball. This accumulation is usually seen in individuals with trichophagia, the compulsive eating of hair, often associated with hair-pulling disorder (trichotillomania). Because hair cannot be broken down, the strands become matted together by mucus and food residue, forming a dense mass that can grow large in the stomach.
The enzyme-resistant nature of the hair causes it to become trapped in the folds of the stomach lining, resisting the normal propulsive force of peristalsis. As the mass increases in size, it can take the shape of the stomach. If it extends a tail-like segment into the small intestine, it is referred to as Rapunzel Syndrome, an extremely rare form of trichobezoar that signifies a potentially life-threatening blockage.
A trichobezoar can cause symptoms such as chronic abdominal pain, nausea, and a feeling of fullness after eating small amounts of food. The presence of this undigested mass can lead to serious complications, including ulceration, bleeding, or a complete mechanical obstruction of the stomach or bowels. Treatment for this condition almost always requires surgical or endoscopic removal of the hairball, followed by psychiatric care to address the underlying compulsive behavior.
Symptoms That Require Medical Attention
Although most single strands of hair pass without incident, any foreign object in the digestive tract carries a minimal risk of causing a complication. Seek immediate medical attention if they experience symptoms that suggest a gastrointestinal obstruction or other serious issue. Specific warning signs include persistent, severe abdominal pain or cramping that does not resolve, especially if localized to one area.
Recurring vomiting or an inability to keep down food and fluids is a serious indicator that the passage is blocked. An inability to pass gas or have a bowel movement, or a significant change in normal bowel habits, also suggests a potential blockage that requires prompt evaluation. Unexplained weight loss, loss of appetite, or an abdominal mass that can be felt are symptoms associated with chronic accumulation and should be discussed with a healthcare provider.