All you need is some vinegar and a plastic bag.
As Melissa Maker, the cleaning expert behind popular YouTube channel Clean My Space, explains, simply fill half of the bag with vinegar and place it over the shower head, making sure it’s submerged. Secure with a rubber band or zip tie and leave overnight.
In the morning, remove the bag and run the shower for a couple of minutes before using. All the gunk that has built up over time will fall away.
For detailed instructions, watch the video below.