If you don’t take away your piercing bar for too long, it may become difficult to unscrew it.
That happens because of water, soap, grease, sweat at other bodily liquids coming into the screw and cementing it.
To unscrew a stuck piercing, first use a needle to remove as much dirt as possible. Try not to scratch the jewelry surface, though. Now punch a hole in a sheet of paper and put the piercing through it, so that the paper cover your body. Now use some WD-40 onto the stuck screw. WD-40
is basically kerosene and oil sparkling mix. Kerosene molecule sizes allows it to get into tiniest cracks and dissolve rust and dirt. WD-40 is not too harmful for the skin, so you may omit the paper part. Spray every ten minutes and wait for half an hour.
How cover pliers tips in PVC tape. The tape will prevent the pliers teeth from damaging the jewelry surface. Get a grip and rotate hard.
Now go and wash away WD-40 from skin with soapy water.
Clean the piercing bar. To avoid stucking in the future, scratch the screw with pencil tip. The graphite will oil the screw, so it won’t cement. It is also recommended to unscrew the bar twice a month.