Despite its growing popularity among drug warriors, hair testing remains one of the most flawed testing platforms in use. It works by detecting drug metabolites passively diffused from the blood stream to the base of the hair follicle. With a pencil-thick sample about an inch and a half long, hair-test labs can detect drug use within the past three months-including patterns of use, such as if you smoked pot, stopped for a month and then smoked again.

For those with very short hair, labs will take a sample from any available part of the body. "Hair is not ready for prime time and it probably never will be," Maltby explains. "The problem with hair testing stems from the very low concentrations that they look for-traces of drugs that are at least two orders of magnitude lower than urine testing. So if the hair is not absolutely clean-if there's the smallest microscopic trace of drugs left on the hair after washing-it will cause a false positive because the true positive concentrations they're looking for are so low."

Maltby insists that the hair-test industry is fully aware of the problem. "They tried for 10 years to develop a washing program that is sufficiently thorough to avoid false positives," he says. "They simply can't do it."

Environmental contaminants are the big problem for hair testing. Microscopic amounts of smoke and powders cling to the hair shaft and wind up as a trace amount on a false-positive hair test. To make matters worse, contaminants cling to dark, coarse hair much more readily-making African-Americans, Latinos and Asians significantly more susceptible to a false-positive result. According to one report, people with dark hair are 10 to 50 times more likely to test positive for drug use from a hair-follicle drug test.

"If the hair-test industry can't get white people's hair clean, then they'll never get black people's hair clean," Maltby says bluntly, "which means they have a racial-discrimination problem."

Aside from abstinence, the best way to beat a hair test is to use one of the many follicle shampoos available from a variety of retail outlets on the Internet and elsewhere. Shampoo manufacturers used to guarantee good results until recently, when revised testing standards significantly lowered the cutoff on hair tests. These new standards are not federally mandated (yet) and not all labs have adopted them (yet), but there's currently no way to determine which cutoff a lab will use. Shampoo manufacturers have begun reformulating their products to once again guarantee effectiveness, but until this next generation of products emerges, the original follicle shampoos remain the best (and only) option for stoners facing the hair scare.