Joanne L. writes:
Hi Robert, I was wondering if you have any thoughts on the following – a short course student of mine works in an essential oil / fragrance suppliers. Recently she poured an unspecified amount of Lemon Scented Myrtle oil over her leg into her shoe which she continued to wear for a number of hours until the end of the day. Her foot and leg turned an orangey red for over a week until she went on holiday and swam in the pool. The same student also spilled lemongrass oil onto her arm at another time. This also turned orangey red but cleared up within a few days. I assume the aldehydes play a part in the discolouration but wonder why the LSM would stain the skin for such a long time?. (I have recommended that she takes milk thistle on a regular basis!)
Wow, tough question Joanne! I have never come across this before. Certainly there is a link between lemon-scented myrtle and lemongrass, as they are both very high in citral (about 90% and 80% respectively). The orange-red skin sounds very much like an excess of beta-carotene, and can be caused by eating a LOT of carrots. In the body, beta-carotene is metabolized into retinol, then retinaldehyde (a form of vitamin A) and then retinoic acid. Citral inhibits the enzyme (ALDH1A2) that carries out this last stage (retinaldehyde > retinoic acid). That’s what normally happens. However, if in this person the citral instead inhibited the initial stage of metabolism (beta-carotene > retinol), then an excess of beta-carotene could build up in the skin, so long as some citral was still there. Rather than an individual difference, it’s also feasible that a massive amount of citral might overwhelm metabolic pathways, leading to a “traffic jam” that has the same end result. It’s not a perfect explanation, but it highlights the only link between those essential oils and beta-carotene-like skin. It does not sound like a phototoxic reaction, since these only happen on exposure to sunlight, they don’t spontaneously clear up very quickly, and the discoloration is patchy and tanned rather than orange. But I think that would be the only other possibility.