Do you remember that science experiment in primary school?
ou would take an empty soft drink bottle, fill the bottom with bicarbonate of soda and then pour in vinegar.
Both perfectly harmless ingredients, but put them together and you had an explosive mess.
On their own, some synthetic chemicals aren't necessarily highly toxic.
Sometimes, it can be the other ingredients paired with them that make them more harmful.
Others can have an accumulative effect in the body that may not be harmful in small doses, but over time, combined with the many other products you may be using, the negative effects begin to be felt.
This is a quick-reference guide for some of the worst offenders on the ingredient list that I steer clear of. You can find out more in my ebook, The Healthy Glow.
These usually start with a prefix of butyl, methyl, ethyl, isobutyl, propyl etc. Parabens have been linked to endocrine disruption and allergens in European studies.
Mineral Oil
Sounds pretty natural, right? Mineral Oil is petroleum by-product, a yucky ingredient that clogs pores and can be contaminated with all kinds of impurities. Also known as paraffin, or paraffin oil. I also avoid anything with a petro prefix as it is a petroleum by-product.
This is a term that prevents companies from having to disclose the ingredients, as fragrance is considered a 'trade secret'.
Code for what can be a chemical cocktail of over 3000 ingredients. I generally avoid products with this listed on the label (unless specified as a natural source), as companies with a green, natural, non-toxic and/or organic focus are quite willing to be transparent. If the rest of the list looks good, however, it is worth contacting the company for details of the fragrance source (synthetic or natural)    
A known human carcinogen, this is usually an ingredient found in nail polish. It is also irritating to the mucous membranes. 
FD&C or D&C Colours
Followed by a number, these synthetic colours are believed to be cancer-causing. I avoid anything containing these colours.
Nail Polish
Whilst this isn't an ingredient, it's something I feel I should add to this list.   You can read more about my views on nail polish here and see a list of nail polish brands that DO and DON'T contain a carcinogenic ingredient.  There are many, many more that I do not use, but as a general rule of thumb, if I can't identify it from a natural source, I won't use it. If you would like more in-depth information regarding these ingredients, check out the Websites I Love page.