Hair drug testing is a method used to check whether someone has used drugs over the past few months. Instead of testing urine or saliva, this test uses a small sample of hair, usually cut close to the scalp. As hair grows, traces of drugs can become trapped inside it, creating a timeline of substance use. Hair tests are often used by employers, courts, or rehabilitation programs because they can detect drug use for a longer period, typically up to 90 days, compared to other types of tests.
How Does a Hair Drug Tests Work?
A hair drug test checks for drug traces that get trapped inside the hair shaft as it grows. When someone uses drugs, small amounts enter the bloodstream and reach the hair follicles. As new hair forms, these traces become part of the hair structure and stay there for a long time.
Basic steps:
- A small hair sample is cut close to the scalp.
- The sample is sent to a lab.
- Technicians wash, prepare, and test the hair.
- Results show drug use over the past up to 90 days.
What Does a Hair Drug Test Look for?
A hair drug test looks for traces of specific drugs that stay in the hair shaft after they enter the bloodstream. These tests can detect drug use over a longer period than urine tests. Common substances they screen for include:
- Marijuana (THC)
- Cocaine
- Opiates (like heroin or morphine)
- Amphetamines
- PCP
What Is a Hair Drug Test Sample?
A hair drug test sample is a small amount of hair collected from a person’s body to check for drug use over time. The hair is usually cut from the scalp, close to the skin, because this area shows the most recent growth. If scalp hair isn’t available, body hair may be used.
Why Do Employers Choose Hair Drug Tests?
The main reasons why employers prefer hair drug tests are:
- Detect drug use over a long period (up to about 90 days).
- Harder to cheat or tamper with than urine tests.
- Simple and non-invasive collection process.
- Provides consistent and accurate results.
- Helps maintain a safe and drug-free workplace.
What Are the Drawbacks of a Hair Follicle Test?
Hair follicle tests are very accurate and can detect drug use over a long period, but they also come with some important downsides.
- Higher cost: They are more expensive than urine or saliva tests.
- Long detection window: Even one-time use can show up weeks or months later.
- Slow results: Lab analysis can take several days.
- Limited to past use: They cannot detect very recent drug use.
- Possible external contamination: Hair can sometimes pick up drug particles from the environment.
How to Test a Bald Person?
If someone has little or no hair on their head, a hair drug test can still be done using body hair. Labs can collect hair from areas like the arms, legs, chest, underarms, or even facial hair. Body hair grows more slowly than head hair, so it may show drug use over a longer time period. However, the results can be less precise because body hair grows at different rates. If no suitable hair is available, the testing facility may choose a different type of drug test, such as urine or saliva.
Can You Cheat a Hair Follicle Test?
It is very hard to cheat a hair follicle drug test because the test looks for drug traces inside the hair shaft, not just on the surface. Washing, dyeing, or using regular shampoos usually will not remove these traces. Some products claim to help, but results are not guaranteed.
How Far Back Can a Hair Drug Test Detect Drug Use?
A hair drug test can usually detect drug use for up to 90 days. As hair grows, tiny traces of drugs stay trapped inside the strands. Since hair grows about 0.5 inches (1.3 cm) per month, labs typically test the first 1.5 inches from the scalp to check for drug use over the past three months.
