Candidates are strongly advised not to apply mehndi or henna on their hands (specifically the palm side) prior to the exam. SNAP uses digital fingerprint scanning for biometric verification at the test center. Henna can interfere with the scanner's ability to capture a clear print, which may result in the candidate being barred from taking the test. If your fingerprints cannot be digitally scanned due to henna, you will likely not be permitted to enter the lab.