When we think about health diagnostics, blood tests and medical scans often come to mind. Yet an often-overlooked window into our well-being lies right on our heads—our hair.
Beyond its aesthetic appeal, hair can serve as a biological archive, capturing a wealth of information about our body’s internal state.
Your hair may hold secrets about your health—including traces of stress hormones, nutritional gaps, and even heavy metal exposure locked within each strand like rings in a tree. It’s a premise that’s driving direct-to-consumer companies to market hair analysis tests. However, medical experts say the science behind them isn’t ready for widespread use.
“Hair tests can be accurate, if they are handled appropriately,” Dr. Joshua Nogar, director of the division of medical toxicology at Northwell Health in New York City, told The Epoch Times.
However, many factors can affect hair test results and that there still aren’t enough data to interpret them reliably, he said.
Researchers continue to explore hair’s potential as a diagnostic tool, and recent advances in hair analysis have opened new avenues for understanding how factors such as stress, nutrition, and substance use might influence overall health.
The Science of Hair as a Biological Record
Hair grows approximately 1/2 inch per month, incorporating nutrients, toxins, and biochemical markers from the bloodstream as it develops. Because hair is metabolically inert once formed, these substances remain locked within the hair shaft, offering a chronological record of physiological changes over time.
Unlike blood or urine tests, which provide a snapshot, hair analysis reflects longer-term exposure and status.
However, since hair takes time to grow, it is less suitable for detecting recent exposures. Nogar noted that it takes approximately one week for drugs, drug metabolites, or chemicals to become incorporated into hair follicles.
“Hair testing cannot detect very recent exposures to drugs and chemicals,” he said.
There is no specific maximum detection period, as it mainly depends on the length of the hair sample being analyzed, Nogar said. For example, certain drug exposures or nutritional deficiencies that occurred more than a year ago may still be detectable a year later, provided that the strand of hair containing that information has not been cut.
“Depending on the substance being evaluated, hair may be useful for chronic exposures or other long-term issues or trends,” Alex Lebeau, a toxicologist, a certified industrial hygienist, and the owner of Exposure Assessment Consulting in Orlando, told The Epoch Times.
Detecting Stress Through Hair Cortisol Levels
One of the most compelling applications of hair analysis is measuring cortisol, the body’s primary stress hormone. Elevated cortisol levels over extended periods have been linked to chronic stress, which can affect cardiovascular health, immune function, and mental well-being.
By analyzing segments of hair—typically the most recent one to three months—clinicians can assess cumulative cortisol exposure, providing insights into how ongoing stress may be affecting a person’s health. This method offers advantages over testing blood or saliva, the characteristics of which can fluctuate throughout the day, making it challenging to gauge chronic stress levels.
However, the testing isn’t ready for widespread use.
Dr. Meena Malhotra, a board-certified physician in internal medicine and obesity medicine and founder of Heal n Cure Medical Wellness Center in the Greater Chicago area, told The Epoch Times that measuring cortisol levels in hair is a relatively new method of assessing cortisol.
“It’s not yet very standardized,” she said.
Nutrition and Mineral Content in Hair
Nutritional deficiencies often leave detectable signatures in hair.
Minerals such as zinc, copper, magnesium, and iron are incorporated into hair during its growth. Lab tests measuring these mineral levels can identify deficiencies that haven’t yet manifested as physical symptoms but could impair immune function, cognitive performance, or energy levels.
Some research has shown that zinc levels can be determined more accurately through hair analysis than through blood testing. Low zinc levels in hair have been linked to compromised immune responses.
Jill Ashbey-Pejoves, a registered dietitian and senior manager of clinical nutrition at Northwell Health, told The Epoch Times that even a mild deficiency in children might not show obvious signs at first.
“More noticeable effects include slower growth and delayed puberty,” she said. “For adults, potential symptoms include changes in taste and smell, a weakened immune system, night blindness, slower wound healing, and various skin problems.”
Monitoring Heavy Metal Exposure
Environmental toxins, including heavy metals such as lead, arsenic, cadmium, and mercury, pose significant health risks. Hair analysis serves as a noninvasive method to monitor exposure levels over time, although interpretation remains challenging because of environmental contamination concerns.
In cases in which elevated levels are accurately detected, they could correlate with neurological problems, kidney damage, or other systemic health issues. Hair analysis can be used to detect heavy metal accumulation patterns, which have been linked to various cancer types, although the technique is still being refined.
However, a limitation to this type of hair analysis is that the detection of some toxic chemicals and metals in hair may not accurately indicate what’s happening inside the body, Dr. Ryan Marino, an emergency physician and toxicology expert at Case Western University, told The Epoch Times.
“For example, bathing and hair products both can affect the chemical composition of hair without indicating any systemic effects,” he said.
Marino also noted that hair analysis is still limited as a tool for determining when someone was exposed to a toxin.
“While there are some methods to try to distinguish [the] timing of exposures, this testing is not usually considered reliable enough to distinguish when an exposure occurred,” he said.
Some tests may pick up false positives or miss certain exposures.
The takeaway, Marino said, is that hair testing should be performed rarely, and only in close consultation with someone specifically trained in toxicologic exposures and testing, who can properly interpret the results.
A Noninvasive Window Into Human Health
Recent research highlights the potential of hair analysis as a valuable tool for assessing nutritional and health status, especially in complex conditions such as inflammatory bowel diseases (IBD).
Micronutrient deficiencies are common in IBD, but diagnosing these deficiencies can be challenging because clinical signs often appear only in advanced stages. Hair analysis offers a noninvasive method to monitor trace elements and mineral levels, providing insights into the body’s nutritional state.
Hair analysis tests may also be used to help improve the diagnosis and treatment of children with autism. One such test uses a single strand of hair to identify biomarkers associated with autism spectrum disorder in infants and young children.
This approach can serve as a timeline of metabolic activity, reflecting exposure to various substances and toxins over developmental periods to gather biological data—potentially allowing for earlier detection and intervention.
Limitations and Future Directions
The integration of hair testing into routine health assessments remains a work in progress. Although hair can serve as a biological archive, capturing information about the body’s internal state, the science of interpreting that information reliably is still developing.
As science advances, hair testing may become an essential tool in preventive medicine, helping people understand and optimize their health long before physical signs emerge. But Nogar said that, for now, hair analysis is still not a reliable way to monitor general health.
