Why can a favourite product suddenly cause my skin to react?
Daniel Maes, vice-president of research and development, Estée Lauder: There may be nothing wrong with the product; it may just be that it is getting to the wrong part of your skin. Products are made to work on or in a specific part of the skin, but if your skin's natural barrier is damaged - from cold weather or over-cleansing, for example - they will not work as well. Then, the ingredients that are meant to be on the skin, such as make-up, can get into the skin and cause a reaction. Using the wrong type of cleanser is a big cause of damage, so switch to something gentle that won't strip your skin.'