Trick question. Both do. Just differently, and you don't have to pick a side forever.
What TENS Actually Does
TENS (transcutaneous electrical nerve stimulation) sends small electrical pulses through pads on your skin, which can interrupt pain signals and may help ease cramping. Genuinely legitimate, not a gimmick, plenty of people rate it highly for period pain.
What Heat Actually Does
Heat increases blood flow to the area and eases the muscle contraction causing the cramp in the first place. Different mechanism. Same drug-free goal.
Where They Differ
TENS needs pads placed correctly and a controller you're actively adjusting. Heat, especially wearable heat like rae, just needs turning on. TENS units are usually device-only, no clothing integration. rae slips into Pocket Undies or any secure waistband and moves with your day. Neither's "better". They're solving the same problem two different ways.
Can You Use Both?
Yes. Plenty of people run TENS during the day and heat overnight, or the other way round. There's no rule that says pick one forever.
What to Check Before You Start Either
Got a pacemaker or another implanted electrical device? TENS is a GP conversation first, not a solo decision. Heat is generally lower-risk, but if pain's regularly derailing your life, that's still a doctor's conversation, not a bigger heat pad or a stronger TENS setting. Shop rae. Read the full Best Heat for Period Days breakdown.