THC can be detected in hair for up to 90 days (about three months) after the last use of cannabis. This detection window is significantly longer than other testing methods such as urine, saliva, or blood tests
Key details about THC detection in hair:
- Detection period: Up to 90 days on average; in some cases, body hair can retain THC metabolites for up to 12 months
- How it works: THC metabolites enter the bloodstream and bind to hair follicles, becoming embedded in the hair cortex as hair grows
- Sample tested: Typically, 1.5 inches of hair closest to the scalp is analyzed, representing about 3 months of growth
- Factors influencing detection time:
- Frequency of use: One-time users may test positive for about a week to a month; chronic users can have THC detectable for longer than 90 days
* **Metabolism:** Faster metabolism clears THC quicker, reducing detection time
* **Hair color and type:** Darker hair with more melanin binds THC more strongly, potentially extending detection time; curly or coarse hair may also retain more THC
* **Hair health:** Healthy hair retains metabolites better than damaged hair
- Hair treatments: Bleaching, dyeing, or perming can reduce THC levels but usually do not eliminate them completely
- Secondhand smoke: Generally does not cause positive hair tests due to washing protocols before testing
Summary
Hair follicle tests are highly sensitive and provide a long detection window for THC, making them a preferred method for employment screenings and legal cases. To avoid detection, abstaining from cannabis for at least 90 days is necessary. While special detox shampoos may reduce THC levels, they do not guarantee passing the test
. In conclusion, THC stays in your hair for up to 90 days on average, with the exact duration depending on individual factors like usage patterns, metabolism, and hair characteristics.
