I'm not sure how I came by YonKa After Sun Lotion Tan Prolonger ($48). Somehow I don't think it came in as a sample, which must mean that I actually bought it. This is a little perplexing since there are a number of things that I don't like about this product. On the other hand, my husband calls me "trigger happy" and keeps threatening to disable Amazon.com's 'one-click'.

What I do like is the texture and smell, and the fact that it has tiny gold glittery bits in it that give a - thankfully subtle - shimmer. At first I liked the fact it wasn't just prolonging my post-South Africa tan, but actually giving it depth. However, after a week of use I was starting to go orange and so was the white towel I was using after my shower. Hmm, not so much a prolonger has a tan in a can. So what is in this stuff?

I had to look no further than the second ingredient (although I have no convincing explanation for not having done this before I started slathering it on). Erythrulose is a sugar that reacts with the amino acids on surface of the skin. Think apple turning brown when exposed to the air. Erythrulose is supposed to be superior to other self-tanning agents, such as DHA, because it doesn't streak. I must admit, I experienced a nicely even tone on my legs and arms. Interestingly, it has not been approved by the FDA as a self-tanner.

On the subject of self-tanning agents, DHA's full name is dihydroxyacetone and this is also used by YonKa. DHA is approved by the FDA. There are reports of skin allergies to it and hairless Mexican dogs used in a study contracted severe dermatitis. Of much more concern, however, is that DHA can make the skin more susceptible to free radical damage from the sun. I've literally only just discovered this and it seems terribly ironic to me. We use fake tan because we want to avoid sun damage but, in reality, we're just making it worse. Oh dear. I kept on reading and it kept on getting worse.

This increased sensitivity to sun damage was concluded by a Korean study in 2007. Forty minutes after the researchers treated skin samples with DHA they found that more than 180 percent additional free radicals formed during sun exposure compared with untreated skin. Erythulose, produced a similar response. And, this study simply confirmed earlier ones. What's more, one of these earlier studies found that dihydroxyacetone also has an effect on the amino acids and nucleic acids that may be carcinogenic.

I believe that the gold sparkle that YonKa was giving my skin comes from the calcium aluminum borosilicate. According to the Environmental Working Group, there is "moderate" evidence that this is carcinogenic and is toxic to organs. Add in the parabens and chlorphenesin, which can cause contact dermatitis and slow down the central nervous system, and I am inclined to let my tan fade naturally.

Granted that there are a few antioxidants in this product, but it seems they have more than got their work cut out for them.

Ingredients in YonKa After Sun Lotion Tan Prolonger

Water, erythrulose, caprylic/capric triglyceride, hydrogenated coconut oil, hydrogenated triglyceride, propylene glycol dicraprylate/dicaprate, glyceryl stearate, cetyl alcohol, grape seed oil, PEG-75 stearate, dihydroxyacetone, red baron root extract, glycerin, bisabol, green tea, white tea, rooibus leaf, lecithin, panthenol, dimethicone, ceteth-20, steareth-20, calcium aluminium borosilicate, PEG-100 stearate, xanthan gum, sodium metabisulfate, tocopheryl acetate (Vitamin E 2%), lavandula oil, thyme oil, geranium flower oil, silica titanium dioxide, retinyl palmitate, acsorbyl palmitate, capryl glycol, carbomer, tin oxide, methylparaben, ethylparaben, chlorphenesin, fragrance, linalool, citronellol, geraniol, limonene, citral, benzyl benzoate, hydroxycitronnelal, eugenol, coumarin.