Why does taking tests apart make them invalid?

Question

I'll admit I've done it a few times but they always look exactly the same before and after I take them out so why is it invalid after? What happens to them?

Answer

And when the air hits it, it makes it dry quicker and shows the evap line

Answer

I think it dries out quicker meaning that you can see the indent line a lot 'darker'. Personally I only notice this happen if I take the test apart and leave it for a while and only on certain tests.

Why does taking tests apart make them invalid?

Let's Glow!

The Top Baby Tracker App: Embrace New Beginnings with Tender Care

The Top Fertility Tracker App: Your Path to Achieving Pregnancy

The Top Pregnancy App: Nurturing Your Journey to Motherhood

The Top Period Tracker for Empowering Your Menstrual Health Journey