Good news - the Buffet serum from The Ordinary does not cause sun sensitivity. There are acids on the ingredient list, but they will not make your skin sensitive to the sun. Some of the included acids are amino-acids (they do not exfoliate the skin, but help attract water to its upper layer. They do not interact with the UV light in any worrisome way). There is also hyaluronic acid - it is safe to use with the UV light as well. Finally, there is citric acid on the Buffet's ingredient list. In substantial concentrations citric acid can cause sun sensitivity - that is why rubbing lemons on your skin is a terrible idea. However, in the Buffet, citric acid is used to adjust the pH of the serum and is in a very low concentration (below 0.01%), and will not cause sun sensitivity.