A hair drug test may identify drug usage how far back in time? Hair drug tests have the greatest detection time, detecting drug usage for up to 90 days. Depending on the medications used, a hair sample can sometimes be used to identify when drug usage began and whether it was ended. In general, however, a hair sample can only tell you what drugs were ingested not when you last used them.
Hair samples can be collected from any part of the body including the scalp, eyebrows, beard, and pubic hairs. Although hair grows at a consistent rate, some areas of the body grow hair faster than others. For this reason, it is important to take hair samples at the same location each time. The follicle remains in one area of the body so if you collect samples from different parts of the body, we cannot combine them to obtain a complete picture of drug use.
During growth periods, hair grows at its usual rate. Between growth periods, your hair is resting or "telogen" phase. As telogen phases approach, their length increases. Recovery periods can range from three months for low levels of medication use to one year or more for high-level use.
A urine drug test can identify drug use in the last few days, while a hair follicle drug test may detect drug usage in the last 90 days. When used properly, these tests can be effective tools for preventing drug abuse within the workforce.
Hair testing works by analyzing the growth of hair cells inside the follicles. The hair shaft is made up of two parts: cuticle and cortex. The cuticle covers the outside layer of the shaft and provides it with its color. The cortex is the core of the fiber where the pigment cell bodies are located.
The cortex consists of three layers. The innermost layer is called the medulla. This is where melanin production occurs. It forms a solid mass that cannot be seen with the naked eye. The next layer out is the endocuticle. This is an outer coating of collagen and elastin fibers that gives strength to the hair. The outer layer is called the exocuticle. It provides moisture to the hair and grows rapidly. Drugs such as cocaine will not enter the hair shaft until after it has grown for several months. By then, it is too late for any type of drug test to detect it.
Depending on the length of the hair strand, drug use can be detected in hair for up to a year after use. Hair testing in substance use monitoring is becoming increasingly prevalent for these and other reasons, including the fact that hair is difficult to adulterate or replace.
Hair testing has many advantages over other drug testing methods. For one thing, it's noninvasive: You don't need to get your subject undressed or put them through any other discomfort-inducing procedures to test their hair. It also provides a record of past drug use, which can help in identifying patterns of abuse or dependence. Last, but not least, hair samples are easy to obtain: There's no need to worry about embarrassing yourself or your subject by asking them to give you a blood or urine sample.
Disadvantages of hair testing include its limited ability to detect recent drug use and the fact that it cannot confirm or deny addiction. Also, since hair growth occurs at a constant rate, even without drug use, comparing results between people will allow for accurate ranking of risk but not necessarily identification of individual users.
In conclusion, drug testing using hair is a useful tool in determining past drug usage and may help identify patterns of abuse or dependence. However, it has limitations and should not be considered a stand-alone method for assessing current drug use or addiction status.