Scrub the crack with a toothbrush to remove any built-up dirt inside. Wipe with a dry cloth or vacuum to collect the loosened dirt.
Insert a tube of latex caulk into a caulking gun. Cut the tip off with a sharp knife or pair of scissors. Press a nail into the tube's nozzle to open it.
Align the caulking gun nozzle with the top of the caulk and depress the plunger. Slowly move the caulking gun down as you fill the crack with the caulk.
Wet a rag and wipe caulk so it lays flush on the refrigerator door's surface.
Leave the caulk to cure for up to eight hours or as long as the manufacturer recommends.