Highly stable, simple to collect, and easy to ship and store, fingernails provide a test sample that is at the cutting edge of drug and alcohol testing. Fingernails are made up of keratin, the same material that hair is made of. As the nail grows, substances can pass from the blood vessels below the nail into the keratin fibers where they become trapped. Fingernails are four times thicker than the typical strand of hair and often capture more of a substance than hair can. Biomarkers become locked in keratin fibers along the entire length of the nail, and can be detected up to 3-6 months after drug or alcohol abuse. Environmental exposure to illicit substances can be detected immediately in nail samples. When drugs or alcohol are ingested, biomarkers can be found in nails as early as 1-2 weeks after. The time period during which drug or alcohol ingestion can be detected depends on the substance used, the amount used, and personal metabolism.