3. Hair Dyes
There has been a lot of controversy in recent years over permanent hair dyes and the chemicals they contain. One of the key ingredients is paraphenylenedeamine (PPDA), which is currently found in two-thirds of hair colourants, and has to be mixed with an oxidising agent, such as peroxide, before application. Research published in the British Medical Journal in 2007 warns that the chemical can lead to dermatitis on the face and in severe cases can even cause facial swelling.
If you are not sure about your reaction, always follow the package instructions and test an area of skin before you use the dye for the first time.