How Cheek Swab Paternity Testing Actually Works
Published January 16, 2026 · Medically reviewed by the partner laboratory's medical director, AABB-accredited relationship-testing laboratory
A cheek swab collects cells from the inside of your cheek that contain the exact same DNA as every other cell in your body. The lab extracts DNA from those cells and reads 34 genetic markers. Cheek swab results are identical in accuracy to blood-draw testing — 99.99%+ inclusion or 0% exclusion.
Why cheeks?
The lining of your cheek sheds cells constantly. A soft swab rubbed against the inside of your cheek for 30 seconds collects thousands of these buccal cells. Every one contains a complete copy of your DNA.
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The lab process
Once received, technicians extract DNA from the cells, amplify it using PCR (the same technology used in COVID PCR tests), and read 34 short tandem repeat (STR) markers. Each marker has two values — one inherited from each biological parent. The alleged father's markers are compared against the child's; every marker must be consistent with paternity for inclusion.
How to swab correctly
No food, drink, gum, or brushing for 30 minutes before swabbing. Rub firmly against the inside of the cheek for 30 seconds, rotating the swab. Air-dry for 30 seconds before sealing.