There is a lot of literature that claims formaldehyde is included in nail polish. It is listed as one of the toxic ingredients in the scarily named “toxic trio. When you scratch a bit below the surface, you will find the literature that explains that it is not pure formaldehyde that is included in nail polish, its methelyn glycol which is water and formaldehyde gas mixed together. This is also sometimes called formalin.

Some argue regulations only allow for a small percentage of methelyne glycol to be used in nail polish, therefore the levels of actual formaldehyde gas in nail polish is too low to cause any adverse effects, infact they claim its the same level as you would find naturally in foods (iii) . Additionally, studies have concluded that methleyn glycol is not formaldehyde’s chemical equivalent (iv) hence it wont produce the same effects as if you were exposed to pure formaldehyde gas.

However,  Michelle (who has a PHD in Chemistry by the way!) of science beauty blog Lab Muffin argues that whilst methelyne gycol is the product of mixing of water and gas ” the reaction is reversible – the formaldehyde can react with water to form methylene glycol, but the methylene glycol can also break down to formaldehyde and water again.” [v}.

I am left with questions such as what are the effects of regular application of this chemical? 

It is widely accepted that formaldehyde is an irritant and allergin so you might want to avoid this if you have skin sensitivity or a known allergy. It might not actually be all that great for your nails. Its often found in nail hardener treatments as the  formaldehyde bonds with the keratin that occurs naturally in the nails, making the nails harder. [vi] However, studies show that regular use of this “may make nails brittle and more likely to break or peel”[vii] Formalin cross links proteins in the the  nail resulting in increase in surface hardness and decreased flexibility, which the user  misinterprets as improved strength and durability.  After months of continued use, nail hardeners may eventually increase nail plate hardness and ridgity to the point that brittleness becomes obvious. [viii]