Why is There Cotton in Vitamin Bottles

I looked, thinking it was to keep the insides fresh. No, I was wrong!

The search term: why is there cotton in vitamin bottles

https://www.google.com/search?source=hp&ei=qz5tXf3dJqOZ_QbMvYmQDQ&q=why+is+there+cotton+in+vitamin+bottles&oq=why+is+cotton+in+vi&gs_l=psy-ab.3.0.0i22i30.681599.684752..686256...0.0..0.181.1925.11j8......0....1..gws-wiz.......0i131j0j0i3.Y6YMLK2LlAw

From a DIY Fixer Channel