What is the difference between HEMA and di-HEMA?

What is the difference between HEMA and di-HEMA?
Well, their only similarity is that they are both monomers, and both are used in acrylate-based nail coatings.

They have a very different molecular structure, with di-HEMA being considerably larger than HEMA.

HEMA is hydroxyethyl methacrylate

di- HEMA is Trimethylhexyl Dicarbamate

HEMA is a known high-level allergen.
All acrylates are allergens, but di-HEMA is considerably less so. This is almost certainly due to its molecular size and less ability to penetrate the skin.

They are both safe to use if used correctly, by a qualified nail professional, and in appropriate percentages.

They have both been banned in the UK and EU for RETAIL products. This is due to the high possibility of HEMA causing an allergic reaction when used incorrectly. It would appear that di-HEMA has also been banned, purely due to the perceived connection to HEMA.

Any nail product with these ingredients must be “For Professional Use Only”.