We sifted through some of TikTok’s most loved skincare products and found this brightening and firming oil from Biossance, which has over 1,000 five-star reviews at Sephora alone. Call it meant ...

Lactic acid build-up causes a burning sensation in your muscles during intense exercise. Lactic acid is not responsible for sore muscles the day after exercise, contrary to popular belief.

Like Biossance’s $56 option ... last step in my routine and after all of my actives, like retinol or my lactic acid serums, without any kind of ingredient conflict. I hope I won’t live ...

So you been sprinting, Lily? Just a bit of cramp? So that's the lactic acid building up. When an athlete does too much or runs too vigorously, not enough oxygen can be delivered to the muscles.