The Science of How Fake Tan Works


These days we’re all aware that suntans give you both cancer and wrinkles, so fake tan is the colour du jour. This miracle-in-a-can stains the skin brown through an interesting chemical reaction. The outer layer of your skin, made up of dead skin cells, is permanently coloured. The tan wears away as the skin cells come off. Here’s how it works, and whether it’s safe!

The Chemistry of Fake Tan

Fake tan products you find in stores contain 2-5% dihydroxyacetone, which looks like this:


It starts off colourless, but it reacts with amino acids (particularly arginine, lysine and histidine) in the skin to form a variety of brown compounds called melanoidins.


It’s actually the same chemical reaction as the one responsible for making food like bread and meat turn brown and delicious when cooked. It’s called the Maillard reaction. For the really intense chem nerds, it proceeds like this with DHA (I got a bit lazy, sorry for the shortcuts):


This forms covalent bonds, which means the skin is permanently stained – water, soap and moisturiser won’t wash it off. The skin starts devloping the tanned colour after 2-3 hours, and the reaction continues for the next 1-3 days. The reaction occurs best at moderately low acidic pHs (3-6), so fake tans tend to come in this skin-friendly range. The extent of the reaction is also influenced by the amount of water around.

Application and Aftercare

DHA only penetrates the very top layer of skin (the stratum corneum), which you may know is dead skin cells. This is why fake tans can’t last longer than about a week – that’s about how long it takes for the stained skin to wear off (that’s why if you look up fake tans that claim to last longer than a week or two, you’ll find tons of grumpy reviews – the skin sheds at a similar rate no matter what product you use!).

This explains all the advice given for making your tan look good and wear off evenly:

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Fact-check: What is micellar water and how does it work? An Update


Over the past two years, my post on the chemistry of micellar water with dodgy photographed scrawlings has become one of the most popular, so I thought it was high time to update it with nicer drawings and finetune the explanation of the science.

This also comes in video form – check it out here!

There are tons of micellar waters on the market now, many of them with similar active ingredients.

The essential ingredients in any micellar water are:

  • Water (obviously) and
  • One or more surfactants.

Surfactants are cool ingredients that I’ve written about a lot (including in my guest post on The Toast). They’re useful molecules with a hydrophilic head that’s attracted to water (and repels oil), and a lipophilic tail that’s attracted to oils and grease (and repels water).

Oil and water normally repel each other, so they try to stay away from each other. This means that oil doesn’t dissolve in water (which you’ll know if you’ve ever tried to wash an oily dish), and instead sits on top like a bad toupee.


When surfactants are added to an oily dish, for example, and then scrubbed with water, they help it break up into droplets (emulsion droplets). They surround the oil and “hide” it from the water, allowing it to be smuggled out and washed away to leave a clean surface. Surfactants are the key ingredients in micellar water, as well as in detergent, soap, shower gel, face wash, shampoo and so on. You’ll also find them keeping oil and water happy together in emulsion products like moisturisers and mayonnaise.


So let’s get back to micellar water. When enough surfactant is added to water (more than something called the critical micelle concentration or CMC), the surfactant molecules assemble themselves into clusters called micelles. These micelles are spherical arrangements of surfactant molecules, with the tails pointing in and the heads facing out – this means the hydrophobic tails are protected from the water by the hydrophilic heads. Some brands of micellar water contain oily substances, like Nivea Sensitive 3-in-1 Cleansing Water which contains grape seed oil. In these products, the oily substance will sit in the middle of the micelle, like in the emulsion droplet.

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Fact-check: What’s to blame for the Mentality Nail Polish problems?


Update (2018-12-05): Since Danny of Mentality Nail Polish has generously sent me a cease and desist for defamation as seen in the comments section, I’d like to interrupt your regularly scheduled programming to clarify (even though I think it’s pretty damn clear already) that the causes of the issues are science-based opinion and speculation. 

Welcome to every nail polish lover’s nightmare – nail disease. Wearers of Mentality Nail Polish have been waking up to this horror: mentality-nail-detachment-dmm-nails

mentality-nail-detachment-dmm-nails Thanks to @dmm_nails for letting me use images of her poor nails!

The technical term for this is onycholysis – when your nail detaches from the underlying nail bed. It’s painful, it’s inconvenient, it’s ugly, and you have to wait til it grows out to recover (if it ever does). There are lots of write-ups on the multitude of legal and ethical fuck-ups that Mentality Nail Polish have made in handling this issue, so I’m not going to rehash that in this post (you can read all about it at The Mercurial Magpie and Ashley Is Polish Addicted, amongst others). Like many others, I’ve been racking my brains wondering what exactly went wrong.

Of course, we won’t know for sure until someone gets analysis results back from a lab. Mentality “almost have enough funds” for an analysis now (although they’ve reportedly known about this problem since September last year, and a GCMS can ordered for under $100 and they haven’t even done that, so I’m guessing we’ll hear the results in 2020 or after an injunction?). But since they’re going full Laganja on this one, I’m not holding my breath.


In the meantime, here’s my analysis of all the speculations that have been flying around. Keep in mind that these are just speculative hypotheses and my opinions on them only – they’ll change as we get more complete information (which is pretty tricky, as Mentality have been deleting their posts, and I’m having trouble finding some of their past statements… I’m sure a lot of links I currently have here will die!). As I’ve read more, I’ve changed my mind about 7 times about what I think the most likely cause is. I’ll be updating the possible explanations as they develop.

What we know

  • Indie makers typically buy a pre-made base from a larger manufacturer, then add tints and glitters. This is what Mentality have supposedly been doing.
  • From Mentality’s Facebook page:
    • Mentality were using Tevco and Fiabila base (3/4 free), but sometime late last year/early this year they switched to a base from Arminex (5 free – parent company of Nubar). They’ve since switched back. They do not make nail polish base themselves… “yet”.
    • The problematic polishes aren’t isolated to the neons, although the neons were very popular and consumed whole barrels of the base, so they’re the most commonly reported.
    • Mentality degassed all the bases to “remove air bubbles and found that Arminex base is very foamy, compared to the other manufacturers whose polish base does not foam upon degassing.”
    • Not everyone who wore them were affected (around 40 people have reported reactions to Mentality so far). The earliest case was @spilledmilknails, a Mentality swatcher, in September 2014.
  • From people who own the affected polishes:
    • The polishes with the different base smell very “chemical” “like melted plastic”, and the smell seems to have gotten worse over time.
    • Some people were reporting stinging, itching and redness upon application.
    • People who experienced nail detachment generally wore them for longer periods, while swatchers who removed them immediately were generally affected less. There are exceptions though – apparently someone swatched them for 4 hours and ended up with nail damage a few days later.

Faulty Arminex Base Theories

This is the angle that Mentality have been pushing, which makes sense because it means less liability for them and hence their best chance of getting out of this without being buried in a steaming turdpile of legal troubles.

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Fact-check: How does IBX Nail Strengthening Treatment Work?


If you’re in the nail world, you’d have heard of IBX, the nail strengthening treatment that’s been saving nails everywhere. How does it work, you ask? Here’s the science!


What is IBX?

IBX is a nail strengthening treatment described as “a penetrative, curable monomer system”, developed by Famous Name, a company headed by the ex-CEO of CND and his wife. It consists of two bottles of liquid containing monomers, small molecules that can join together, as well as a photoinitiator which starts their joining when the right type of light is used. First, IBX Repair is applied to the visibly damaged parts of the nail and cured, then regular IBX is applied to the nail and cured. The results look pretty amazing:


As well as healing splits and peels, it also fills in grooves and adds a protective layer to your natural nail so it can grow out further without breaking, and shields it from further abuse, like gel polish removal. Pretty awesome, right? Turns out that the way it works is pretty nifty too! (I’m not getting paid to write this by the way – just sayin’.)

How does IBX work?

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Fact-check: Does Tea Tree Oil Work?



Tea tree oil is probably something you’ve seen at the beauty counter dozens of times, in skincare creams and ointments. But what is it used for?

What’s tea tree oil?

Tea tree oil comes from the leaves of the Melaleuca alternifolia shrub (common name tea tree, surprise surprise!). This tree is native to Eastern Australia. The oil is colourless to light yellow, and smells strongly pine-like. If eaten, it’s poisonous to both humans and animals.

In skincare, tea tree oil is useful because it’s antibacterial – pimples contain the bacteria Propionibacterium acnes (commonly abbreviated as P. acnes), and killing these reduce acne (many other acne treatments, like benzoyl peroxide and the antibiotics clindamycin and erythromycin, also directly kill acne bacteria). It also kills fungi, which means it’s handy for nail and foot infections too.

How do I use it?

If undiluted, tea tree oil can be irritating, so diluting it in another oil like mineral oil or sunflower oil is the best way to use it. A study found that 5% tea tree oil works as well as 5% benzoyl peroxide – it acts more slowly, but it’s less irritating, so 5% is a good starting point if you’re not sure.

5% tea tree oil means if you want a total of X mL tea tree oil mixture, to get the mL of:

Tea tree oil: multiply the total X by 0.05
Diluting oil: multiply the total X by 0.95

Then mix the two together in a clean bottle to get your mixture!

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Fact-check: The Lead in Lipstick is Safe



This “lead in lipstick” hoax has been going around Facebook again – it’s actually pretty ancient (goes back to the early 2000s) and refuses to die. Here’s one version:


All the versions of this chain email are slightly different but all have the same themes… and all are BS. There’s a whole bunch of wrong in this scary-sounding PSA.


Recently a brand called “Red Earth” decreased their prices from $67 to $9.90.

This bloody factoid changes currencies all the damn time – let’s pretend it’s in Australian dollars, cos it’s probably the way it’ll make most sense. Red Earth was never $67, and it sure as hell isn’t $9.90 now. Even if you don’t know science, you should know that Red Earth is a comfortable $24.

Why? Because it contained lead.

This is true. BECAUSE EVERYTHING CONTAINS LEAD. The thing is, atoms and molecules are really really really really really really ridiculously tiny. According to some maths, each of us contains about 200 billion of Shakespeare’s atoms (and 200 billion atoms from anyone else who’s ever lived and been dead for a while), so it’s not surprising that in your lipstick, there’s at least one atom of an element that was spewing into the atmosphere for 80 years thanks to leaded petrol. So a “trace amount of lead” is unavoidable in everything outside of the most high tech, fanciest lab.

So the real question is, how much lead is there? They’ve got one thing right:

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Do oils make your skin less oily? The myth of rebound oil

You’ve probably seen the concept of rebound oil production, or reactive seborrhea: “shampoos… strip the scalp of its natural oils and cause the scalp to overproduce oil to compensate” “our skin naturally regulates perfect oil production” “your skin will have to adjust to producing less oil” “the oil tells the skin it’s no longer drying out, which helps to control …

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Fact-check: “Solvent-Free” Nail Polish Removers

For years, we’ve been using just 2 solvents, ethyl acetate and acetone, to remove nail polish. But recently a whole host of new removers containing neither of those have made their way onto the market – what are they, and are they worth a shot? Are they really solvent-free? No. Anything that dissolves something else up is a solvent – …

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