Effects of henna dye on oxygen saturation reading using pulse oximetry.

P oximetry is a non-invasive method that uses the spectrophotometric principle to monitor oxygen saturation in the blood. It produces a plethysmographic wave from which oxygen saturation is obtained.1 It is has become increasingly used in outpatient clinics and emergency rooms in addition to its use in critically ill patients and during anesthesia.1 Although it is an accurate method in reflecting oxygen level in the blood, its reading can be influenced by several conditions, including poor peripheral perfusion, carboxyhemoglobinemia, methemoglobinemia, and anemia. Henna is a cosmetic dye that is made from special leaves (Lawsonia inermis), which grow in hot climates (North Africa, Asia and Middle East). It is very popular in Saudi Arabia, the Middle East, and Indian subcontinent and is used in dying the skin and hair. Recently, it has been sold in the west as a form of transient tattoo. It is particularly used in dying the skin of the hands and feet. The natural henna when used to dye the skin gives an orange-red color. However, when combined with synthetic dye it produces a black color. Studies have shown changing the color of the skin in hyperbilirubinemia,2 and hyper-pigmentation3 may influence the reading of pulse oximetry. Similarly, White and Boyle4 demonstrated that applying nail polish to the nails can affect the accuracy of pulse oximetry readings. Therefore, it is possible that dying the fingers and toes with henna can give an erroneous pulse oximetry reading. However, we found only one study in the literature examining the effect of henna on pulse oximetry.5 In this prospective study we have addressed this issue, and studied the effect of natural henna on the reading of pulse oximetry. We recruited 104 healthy individuals (mean age 32.93; 16% male and 84% female) with normal oxygen saturation at room air. In addition, 14 patients (mean age 42.5; 6 male and 8 female) with hypoxemia on room air were enrolled. The study was explained to all subjects and consent was obtained. For the purpose of this study, hypoxemia was arbitrarily defined as oxygen saturation less or equal to 91%. The study was approved by the ethical committee of our institution (King Khalid National Guard Hospital), where the study was conducted. The study was explained to all Figure 1 The effect of henna on oxygen saturation in hypoxic patients measured by oximetry. Results expressed as median; *stand for p<0.01.