The most common way to collect DNA is a buccal (cheek) swab, which takes about 30 seconds and requires no needles or special training. But cheek swabs are just one option. DNA can also be collected from saliva, blood, hair, and even skin cells left on surfaces. The best method depends on why you’re collecting the sample and how much DNA you need.
Cheek Swabs: The Standard Method
Buccal swabs are the default for home DNA kits, paternity tests, and many clinical genetic tests. The process is simple: rub a foam-tipped or cotton swab along the inside of your cheek for at least 10 seconds per side, pressing firmly enough that you can see the outline of the swab pushing against the outside of your cheek. This pressure is what dislodges the cells lining your inner cheek, which contain a full copy of your DNA.
Before swabbing, remove any gum, candy, or food from your mouth. Most protocols recommend avoiding eating, drinking, or smoking for at least 30 minutes beforehand, since food particles and chemicals can contaminate the sample or dilute the cells you’re collecting. Use a fresh swab for each person and never reuse one.
If your kit includes an FTA card (a special paper that preserves DNA on contact), you’ll press the swab onto the pink sample area using a side-to-side motion until the pink turns white. Let the card dry at room temperature for at least 10 minutes. If you’re using plain sterile swabs instead, place them back into their original packaging and let them air dry completely before sealing. Never store swabs in plastic bags or airtight containers while still damp, as moisture promotes bacterial growth that degrades the DNA.
Saliva Produces the Highest DNA Yield
If you’ve used a consumer genetics service like 23andMe or AncestryDNA, you collected saliva rather than a cheek swab. There’s a good reason for that. A comparison published in the American Journal of Human Biology found that whole saliva samples yielded an average of about 155 micrograms of DNA, compared to roughly 11 micrograms from a standard cheek swab. That’s more than 13 times as much genetic material.
Saliva also produces higher-quality DNA. The saliva and oral rinse methods both achieved near-perfect amplification rates (98 to 99%), meaning almost all samples were usable for genetic analysis. Cheek swabs and cytobrush samples had notably lower quality scores and amplification rates averaging 75 to 84%. For large-scale research studies or tests that need generous amounts of clean DNA, saliva collection kits with built-in stabilizing fluid are the preferred choice.
The tradeoff is convenience. Saliva kits require you to spit about 2 milliliters into a tube, which can take a few minutes and isn’t always practical for young children or people with dry mouth. Cheek swabs are faster, easier to standardize, and work well for straightforward tests like paternity or identity verification where less DNA is needed.
Blood Samples for Clinical and Research Testing
Blood draws are common in hospital and research settings where DNA collection is part of a broader workup. A standard collection requires 4 to 5 milliliters of blood, drawn into a specialized tube containing a chemical that prevents clotting. White blood cells are the source of DNA in blood (red blood cells don’t have a nucleus).
Blood samples generally yield high-quality DNA, but the collection requires a trained phlebotomist, proper tubes, and a cold chain for transport. For most genetic testing purposes, saliva or cheek swabs have largely replaced blood draws because they’re noninvasive and can be done at home.
Collecting DNA From Hair
Hair can be a DNA source, but only under specific conditions. The hair shaft itself, the visible strand you’d pick up off a pillow, contains very little usable nuclear DNA. What matters is the root. A hair pulled from the scalp with its follicular tissue still attached (the small bulb at the base) contains enough cells for standard DNA profiling.
If no follicular material is present, the hair can still be tested using mitochondrial DNA analysis, which examines a different, smaller portion of the genetic code. Mitochondrial DNA is inherited only from your mother and is less individually specific, so it’s useful for identifying maternal lineage but cannot distinguish between siblings or other maternal relatives. In forensic cases, hairs without roots are typically sent to specialized labs equipped for this type of testing.
Touch DNA: Skin Cells on Surfaces
Every time you grip a doorknob, tap a phone screen, or handle a tool, you leave behind skin cells carrying your DNA. Forensic investigators routinely collect this “touch DNA” from crime scenes, and the techniques vary depending on the surface.
For hard, nonporous surfaces like glass, metal, or plastic, a single moistened swab rubbed across the area is the standard first approach. It’s versatile, cheap, and effective. When conditions are more challenging, such as very dry surfaces or extremely small sample areas, investigators use the double-swab technique: a wet swab first to loosen cells, followed immediately by a dry swab to pick up what remains. Co-extracting both swabs together maximizes the amount of recovered DNA.
Porous surfaces like fabric or paper call for different strategies. Adhesive tape lifting works well on textured or porous materials, pressing sticky tape against the surface to pull off skin cells. In some cases, analysts simply cut out the relevant section of fabric or material entirely and process the whole piece. A vacuum collection method has also shown advantages on nonporous surfaces, though it’s less commonly used in the field.
Preventing Contamination
DNA testing is extraordinarily sensitive, which means contamination is the biggest threat to a usable sample. A stray skin cell from the person collecting the sample, a sneeze near an open tube, or a reused swab can introduce foreign DNA that compromises results.
The core principles are consistent whether you’re collecting at home or in a lab. Wear fresh disposable gloves and change them between samples. Use only individually packaged, sterile swabs. Never touch the swab tip with your fingers. Keep collection surfaces clean and dry. If you’re collecting from multiple people, handle each person’s sample separately with a fresh pair of gloves.
Professional forensic labs take additional steps: physically separating work areas, using one-way workflows so samples move in only one direction through the process, maintaining positive air pressure in clean rooms, and requiring hair nets, shoe covers, and dedicated lab coats. They also run routine blank tests on their work surfaces to catch contamination before it affects real cases.
Storing Samples After Collection
How you store a DNA sample matters as much as how you collect it. Unprotected DNA degrades quickly at room temperature. Enzymes called DNases, which are present on skin and in the environment, actively break down DNA strands. Moisture and heat accelerate this process.
For short-term storage, keep dried samples (swabs, FTA cards) in paper envelopes at room temperature in a cool, dry place. Paper allows residual moisture to escape. Plastic bags trap humidity and encourage bacterial growth, so avoid them unless the sample is completely dry and you’re adding a desiccant packet. FTA cards are specifically designed to inactivate enzymes and stabilize DNA on contact, making them shelf-stable for years at room temperature.
Liquid samples like saliva kits include a stabilization buffer that deactivates the enzymes responsible for DNA breakdown. These buffers typically work by chelating metal ions that enzymes need to function and by denaturing proteins. A properly stabilized saliva sample can remain viable at room temperature for weeks or even months during shipping. For long-term storage of any DNA sample, freezing at minus 20 degrees Celsius or colder is the gold standard. Under specialized encapsulation conditions, researchers have estimated DNA half-lives of tens of thousands of years, but in practical terms, a well-preserved frozen sample remains usable for decades.