"Anti-perspirants do not work by jamming little particles into the openings of sweat pores in the armpits. That might work if sweat shot out of your body’s sweat pores in miniature geysers, but on the micro-level of the skin, geysers, hoses and all of the other usual ways we think of water emerging from a pore do not exist. Everything’s too small. There’s no way the incipient sweat water could build up a high enough pressure in its sub-surface tubes to flow. This is an odd limitation, but useful. If sweat gushed out of us like water out of a tube, then all parts of our body aiming downwards would be perpetually leaking – feet, armpits, fingertips, and chin, while those aiming up – shoulders, scalp, and little else – would be perpetually dry. Rather, sweat emerges because it’s tugged out. It has a negative electric charge as it hovers in its little beads inside, and as the surface of the sweat pores has a positive charge when excited the result is that the sweat ooze is pulled out. It’s like yanking a sausage from a tight tunnel.

"Enter the aluminum. Falling off from the roll-on anti-perspirant tube, landing on the crushed skin surface newly contoured by the pressure of the applicator, it short-circuits the whole sweat-extruding operation. Aluminum flecks, which are the key ingredients in anti-perspirants, are negatively charged. That means the extra furry cloud of negative electrons they carry around with them counterbalances the normal positive charge on the skin surface. There’s no pull on the sweat sausage any more. The aluminum is even more likely to have a little left over to poke down the sweat pore tunnel and electrically repel the negatively charged water waiting deeper inside—like a hand pushing the tunneled sausage deeper. There’s a crackle, some static, the equivalent of sparks, and the whole system is shut, short-circuited and out of operation for hours. the sweat caught inside dissolves back into the body, crumbling through cracks in the sweat tubes like water from a leaky hose."