I did a lot of research before purchasing this product and I was really looking forward to seeing the benefits mentioned by others. But sadly, this was not the case. I choose to apply the serum at night after cleansing. Within 5 minutes my face looked as through I has an EXTREME sunburn and it was rapidly heating up. I chose not to wash the product off but rather wait and observe what happens. After about 3 hours the flush and heat subsided. The next morning my skin was back to normal. I applied this product every 2nd night for 1 week hoping this reaction would subside but it did not. I have been using Vitamin C 15% and glycolic acids regularly and have never experienced this type of reaction. I do not consider myself to have sensitive skin however I am clearly sensitive to this product. I contacted the company directly to inquire and they said this is absolutely not normal. I also noticed the serum does not look like the picture on cult beauty. Perhaps the product was bad or not genuine. A true disappointment and a large waste of money. I didn't even notice the slightest improvement in skin within the week whereas other products I have I can clearly see benefits and improvements. I would not recommend this product.