Many parents know the frustrating and perplexing experience of going to change their baby in the morning only to find that their diaper isn’t even completely full, but their skin is damp and they’ve got the beginnings of a little diaper rash that wasn’t there when they went to bed. So, what gives?

Well, a lackluster diaper rewet rate could be to blame. There’s a few key factors that go into diaper performance—liquid retention capacity (how much liquid a diaper’s core can absorb and hold), liquid strike-through speed (how fast liquid passes through the layers of diaper material into the core), and rewet rate (once that liquid absorbs, how well it stays locked in the diaper’s core, away from delicate skin).

When diapers are tested for performance, the rewet rate is determined by measuring how much liquid comes back to the diaper’s surface after it’s been absorbed into the core and put under pressure—mimicking real-world circumstances of your baby putting pressure on the diaper’s core with regular wear and movement. A lower rewet rate is better, and means the diaper’s surface that touches your baby’s skin is drier; a higher rewet rate indicates that more moisture is sitting against baby’s skin.

If moisture spends extended periods of time in contact with skin, it can alter skin’s pH and compromise its barrier. A baby’s skin barrier is already thinner and more delicate than an adult’s, so their skin is even more sensitive to things like friction and wet and dirty diapers. So the ability to keep moisture away from baby’s skin, especially for long stretches overnight, can really make all the difference between a baby waking up soggy, leaky, and rashy, and them staying dry and comfy until morning.

Why does absorption speed matter for your nighttime diaper?

Diaper absorption speed is the rate at which a diaper pulls liquid into its core. When diapers are tested for performance, the absorption speed is measured via strike-through time.