Some people may experience a mild tingling sensation after applying the serum, and this is normal. As the Tremella Fuciformis (Hyualronic Acid) penetrates deeply into the skin with it's hydration. You can try applying a lesser amount (2-3 drops) or doing so with less frequency to allow your skin becomes accustomed. If you're feeling an intense burn, or the sensation becomes painful; discontinue use and seek advice of your medical professional. Our products are gentle for all skin-types, but individual cases may vary, so we always recommend doing a patch test before full application.