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Drs. Martel and Anderson ("Decorating the 'human canvas': Body art and your patients," August 2002) have written an excellent review that is relevant to all providers who care for teenagers. As a fellow in adolescent medicine, I am familiar with both the popularity of, and complications associated with, body art in adolescents, and I would like to draw attention to a popularand safealternative to tattooing that was not mentioned in the article: henna.
Henna is a body paint derived from Lawsonia inermis; powder from the dried plant is mixed with natural oils to form a paste that is applied to skin. Henna stains skin orange-brown for approximately three weeks before it fades.
Henna has been used as a body decoration throughout India, North Africa, and the Middle East for thousands of years. Recently, henna has become more popular in the Western Hemisphere; celebrities such as Madonna, who wore henna in a recent MTV video, have increased US teenagers' awareness of this type of body art, which is an ideal form of expression for adolescents because it is safe and temporary.
Allergic reactions to pure henna are rare, although a patch test of henna can be applied to check for an allergy. Severe contact dermatitis from henna has been reported, but all these reactions have been found to be caused by chemicals, such as p-phenylenediamine, that were added to henna to make the stain darker (LeCoz CJ et al: Arch Dermatol 2000;136:1515). Other minor skin reactions may be the result of the eucalyptus oil that is sometimes mixed with henna to promote absorption through the skin.
A potentially severe side effect of henna is related to its oxidative properties. In the Middle East, where henna is often applied to infants and where glucose-6-phosphate dehydrogenase (G6PD) deficiency is common, there have been some reports of henna temporally associated with hemolytic crisis and hyperbilirubinemia in infants and young children with this enzyme defect who were decorated with henna (Raupp P et al: Arch Dis Child 2001;85:411). No cases of henna exposure associated with hemolytic crisis in teenagers with G6PD deficiency have been reported. Because of the oxidative potential of henna, however, it should probably be avoided in patients who have a G6PD deficiency.
That warning notwithstanding, henna is still much safer than a traditional tattoo. Because needles are not used to apply henna, there is no risk of viral or bacterial infection. Furthermore, there is no need to worry about the scarring or expense of removing a permanent tattoo, as henna persists on the skin for only a few weeks.
The authors reply: We thank Dr. Olshen for her kind comments and for the excellent information she has provided. Shortly after the article was published, we also became familiar with the use of henna as a safer alternative to tattooing. Because henna may be contaminated with other ingredients without the patient's knowledge, we agree that patch testing before use is ideal.
Regarding the article "Liquid mercury: A poisonous plaything" (August 2002), how much mercury is needed to be considered hazardous when it vaporizes?
The author replies: It depends on many variables, such as the location of the spill (indoors?), the size of the room, how the spill was cleaned up (vacuumed?), and the temperature in the room. Having said all that, here are some numbers that can serve as a general reference: One fever thermometer contains 1.59 grams of mercury (for comparison, one liquid teaspoonful of mercury contains 66.8 grams). In a room 4 meters by 4 meters by 2 meters that is minimally ventilated, the mercury in that one fever thermometer can generate 49.69 mg/m3 of mercury vapora value that greatly exceeds the Agency for Toxic Substances and Disease Registry (ATSDR) minimal risk level (MRL). ATSDR MRL values for mercury and many other chemicals are available at www.atsdr.cdc.gov .
Readers' Forum. Contemporary Pediatrics 2002;11:127.