Whether you’re a casual cannabis user or someone who’s just tried an edible at a weekend party, you may be wondering:
How long does THC stay in your hair?

The answer might surprise you—because when it comes to drug testing, your hair is like a time capsule. While THC may leave your bloodstream or urine within days or weeks, it can linger in your hair for months.

Let’s break down how THC ends up in your hair, how long it sticks around, and what that means for drug tests and detox strategies.

🧪 First, How Does THC Get Into Your Hair?

When you consume cannabis—whether by smoking, vaping, or edibles—THC (tetrahydrocannabinol), the main psychoactive compound, enters your bloodstream. As your blood circulates, it nourishes your hair follicles. Small amounts of THC and its metabolites (especially THC-COOH, the main compound tested for) are deposited into your hair as it grows.

Unlike urine or saliva, which show recent usage, hair testing provides a long-term snapshot of cannabis use over time.

⏳ So, How Long Does THC Stay in Your Hair?

Up to 90 days. That’s the standard detection window for most hair follicle drug tests.

Here’s how it works:

• Hair grows about half an inch per month.

• Labs usually test the 1.5 inches of hair closest to the scalp, representing roughly three months of growth.

• If THC is in your system during that time, it’s likely to show up in a test.

If your hair is longer than 1.5 inches, older drug use might be “recorded,” but labs usually only test that recent section unless specifically asked otherwise.

👩‍🔬 Can Secondhand Smoke Cause a Positive Hair Test?

It’s extremely unlikely. Hair tests are designed to detect internal exposure (i.e., THC in the bloodstream), not external contamination. That means you would typically need to consume cannabis—not just be around it—for it to show up in your hair.

🧼 Can You Get THC Out of Your Hair?

This is where things get tricky. Once THC metabolites are in your hair, they’re very difficult to remove. There are tons of detox shampoos and DIY methods on the internet, but none are guaranteed. Lab tests are designed to detect both THC and chemical tampering.

Some people attempt the “Macujo Method” or use detox shampoos like Aloe Rid, but these are:

• Often expensive

• Time-consuming

• Damaging to hair

• Still not 100% reliable

Your safest bet? Avoid cannabis for at least 90 days if you expect to be hair-tested.

🧪 What About Other Types of Drug Tests?

If you’re being tested for THC, here’s how long it generally stays detectable in various types of tests:

So if you’re concerned about passing a hair follicle test, it’s wise to think long-term—because your hair remembers more than you might think.

💡 Final Thoughts: Plan Ahead

Hair tests are no joke. They’re often used by employers, government agencies, or in legal cases where a longer detection window is desired. Even if you last used cannabis months ago, it can still show up in your hair test.

The best way to ensure a clean result? Abstain for at least three months before the test. No detox product is foolproof, and attempting to cheat the test may raise red flags.

THC might leave your body in a few days—but your hair tells the whole story.