TL;DR
The dirty part of a pizza cutter is not the blade -- it is the axle and the underside of the blade guard, where melted cheese collects and hardens out of sight. Wash it in hot water with a degreasing dish soap, rotating the wheel under the tap so water reaches the hub, and always work with the blade edge turned away from your hand.
Handle the wheel safely
A pizza wheel is a circular blade with no handle position that guarantees your fingers are clear. That makes it one of the more common kitchen tools to cause a cut during washing rather than during use.
Three rules cover it.
Hold the handle only. Never grip the wheel to steady it, and never wipe along the edge with a bare finger or a thin cloth.
Direct water at it rather than reaching for it. Rotate the wheel by touching the flat side, not the rim.
Never put it in a sink of soapy water. A pizza cutter hidden under suds is the classic way this goes wrong. Wash it as its own item and set it down immediately afterward.
If your cutter has a blade guard or a cover, keep it in place while washing whatever you can, and remove it only when you need to clean underneath.
Why the axle is the problem
Melted cheese is fat, protein, and moisture. When it cools it sets into a rubbery mass that grips.
As the wheel turns through a pizza, cheese is pushed sideways off the blade and collects in the narrow gap between the wheel and the frame -- the axle area. That gap is a fraction of a millimetre in some designs.
The blade guard, which is a curved plate covering part of the wheel, creates a second hidden pocket. Cheese pushed off the blade lands on its underside.
Neither area gets touched by a sponge run over the outside. That is the entire reason a pizza cutter that looks clean can smell stale. Hidden pockets and pivots are the recurring failure point across kitchen gadgets, as covered in the guide to cleaning kitchen tools without damaging them.
How do you clean a pizza cutter?
Rinse it under hot running water while rotating the wheel by its flat side, so water flows through the axle gap. Wash with hot water and a degreasing dish soap, using a small brush at the axle and under the blade guard. Rinse hot, then dry the wheel and hub completely.
The routine
1. Rinse hot, immediately after use. Hot water melts cheese fat so it flows out of the axle. Cold water sets it in place.
2. Rotate the wheel under the tap. Turn it slowly by touching the flat face, letting water enter the gap from both sides.
3. Brush the axle. A small nylon brush or a toothbrush pushed into the gap on both sides while rotating the wheel.
4. Get under the blade guard. Slide the brush along the underside of the guard. On many designs the guard lifts or pivots for access.
5. Wipe the blade edge safely. Lay the wheel flat against a folded cloth or a brush and draw it along the edge, away from your hand.
6. Do the handle joint. Where the frame meets the handle there is a seam that collects the same residue.
7. Rinse hot and dry fully. Water in the axle rusts a carbon steel wheel and stiffens the bearing.
Cutters that come apart
Some pizza cutters are designed to disassemble -- the wheel unscrews or a pin releases, and the blade lifts out of the frame.
If yours does, take it apart every few uses. It is the only way to properly clean both faces of the hub and the inside of the frame, and it takes under a minute.
Lay the parts on a towel in the order they came off. Wash each piece with hot soapy water and a brush, dry every part fully, and reassemble only when everything is dry.
Do not force a cutter that is not designed to come apart. Riveted assemblies are permanent, and prying at one bends the frame so the wheel no longer runs true.
Shears follow the same take apart if it is designed to logic, described in how to clean kitchen shears.
Dealing with hardened cheese
If cheese has set hard in the axle, soak the head of the cutter in hot soapy water for ten to fifteen minutes with the handle propped out of the water if it is wooden.
Hot water alone softens cheese fat well. After the soak, rotate the wheel under a hot tap and brush the gap again.
A wooden toothpick can lift a stubborn lump out of the axle gap without touching the blade edge. Do not use a metal pick, which scratches the hub and can damage the bearing surface.
Avoid bleach entirely. It does nothing to cheese fat, chloride bleach pits stainless steel, and bleach must never be combined with ammonia, with vinegar or any other acid, or with rubbing alcohol, because each of those combinations releases a toxic gas.
Can a pizza cutter go in the dishwasher?
Many all metal and plastic handled cutters are dishwasher safe, and the water temperature deals with cheese fat well.
Place the cutter in a closed cutlery basket or lie it flat and secured, with the blade positioned so nobody reaches over it when unloading. This is the main safety issue with dishwashing a wheel.
Two limitations. Spray does not reliably reach into a narrow axle gap, so rinse and brush it by hand first. And cutters with wooden handles should be hand washed, since heat and detergent dry and crack wood.
Keeping the wheel turning freely
A wheel that has become stiff usually has residue in the axle rather than a mechanical fault. Clean it before assuming it is worn out.
Dry the hub thoroughly after every wash. A carbon steel wheel rusts at the axle first, and rust there seizes the bearing.
Store the cutter with its guard fitted, or in a sheath, both to protect the edge and to protect the hand that opens the drawer.
Replace a cutter with a wheel that wobbles, a nicked edge that tears rather than cuts, or a cracked handle. And keep the surface you cut on in good order too -- stone bakeware has its own separate care rules, in how to clean a pizza stone. Other bladed tools with hidden slots are covered in how to clean an avocado slicer tool.
Cleaning a tool reduces residue and cross contact between foods. It is not a food safety program on its own.
Source: USDA Food Safety and Inspection Service guidance on cleaning food contact utensils
FAQ
How do you clean cheese out of a pizza cutter axle?
Rinse under hot running water while rotating the wheel by its flat face, so water flows into the gap from both sides. Then push a small nylon brush into the axle gap as you turn the wheel. For hardened cheese, soak the head in hot soapy water for ten to fifteen minutes first.
Can a pizza cutter go in the dishwasher?
Many are dishwasher safe, and the hot water handles cheese fat well. Place it in a closed cutlery basket or lay it flat and secured so no one reaches over the blade when unloading. Rinse the axle by hand first, since spray rarely reaches into that gap.
How do you wash a pizza cutter without cutting yourself?
Hold the handle only, never the wheel rim, and rotate the wheel by touching its flat face. Direct water at the blade rather than reaching for it, wipe the edge by drawing it along a folded cloth away from your hand, and never leave it in a sink of soapy water.
Should you take a pizza cutter apart to clean it?
If it is designed to come apart, yes, every few uses -- it is the only way to reach both faces of the hub and the inside of the frame. Never force a riveted cutter apart, since prying bends the frame and the wheel will no longer run true.
Why does my pizza cutter wheel stick?
Usually cheese residue packed into the axle gap rather than a mechanical fault, or rust at the hub from being stored wet. Soak the head in hot soapy water, brush the gap while rotating the wheel, then dry the hub thoroughly before storing.
How do you clean under a pizza cutter blade guard?
Slide a small nylon brush along the underside of the guard under hot running water. On many cutters the guard lifts or pivots away for access. Cheese pushed off the blade lands there and a sponge on the outside never touches it.
Bladed tools take a minute with the right handling. The kitchen after pizza night takes longer. If you would rather hand that off, get a quote or read more about house cleaning services.