As the biological system of each person is different, everyone will be allergic to something. The main ingredients of Lightenex is, Kojic Dipalmutate and Liquorice extracts. Both are tolerated well by the majority of the population, however there will always be a very small percentage of the population who will be allergic to it. As a simple way of testing if you are allergic, you can rub one drop of the Lightenex on the lower part of your hand, twice a day for two days. If there is any irritation or darkening of the skin in the area, you may be allergic to either the Kojic Dipalmutate or Liquorice extracts, which are the most effective ingredients used in modern skin whitening products.The darkening of the area is only temporary and the skin will return to its normal colour within one or two days after discontinuing the product. From the research we have conducted for Lightenex, none of our results showed any allergic reactions to our products.