You can physically fit a toothbrush in the dishwasher, but you shouldn’t. The American Dental Association specifically recommends against it, citing heat damage to the brush. Beyond warping and melted bristles, there are less obvious risks involving detergent residue and chemical leaching that make this a bad idea all around.
The good news: safer methods for sanitizing a toothbrush are simple, cheap, and take less than a minute.
Why Dishwasher Heat Damages Toothbrushes
Most dishwashers hit temperatures between 130°F and 170°F during wash and dry cycles. That’s well above the point where the plastics in a typical toothbrush start to soften. Nylon bristles can warp, curl, or melt together, and the handle itself may bend or deform. Even if the toothbrush looks fine after one cycle, the internal structure of the bristles deteriorates, making them less effective at removing plaque and more likely to irritate your gums.
The bristles in most toothbrushes are anchored into the head with small metal staples and a thin layer of adhesive. Repeated exposure to high heat can weaken that bond, raising the chance that bristles loosen and come out in your mouth during brushing.
Detergent Residue Is a Real Concern
Dishwasher detergent is far more aggressive than anything meant to go in your mouth. A 2022 study published in the Journal of Allergy and Clinical Immunology found that professional dishwashers left significant amounts of cytotoxic rinse aid on dishes even after the cycle was complete. The alcohol ethoxylates in rinse aid damaged the protective lining of gut cells in lab models, triggering inflammation and weakening the barrier that separates your digestive system from harmful substances.
A dinner plate has a smooth, flat surface that’s relatively easy to rinse clean. Toothbrush bristles are dense, tightly packed, and designed to trap particles. That makes them especially good at holding onto detergent and rinse aid residue. Putting those bristles in your mouth twice a day means direct, repeated contact with chemicals that were never intended for oral use.
Plastic Leaching Under Heat
The Mayo Clinic advises against putting plastic containers in the dishwasher because heat can break down the material over time, allowing compounds like BPA to leach out. Most toothbrush handles are made from polypropylene or similar plastics, and while not all contain BPA, many contain other plasticizers that behave similarly under heat stress. A toothbrush that goes through a hot dishwasher cycle and then sits in your mouth for two minutes twice a day creates a direct route for those chemicals into your body.
Cross-Contamination Works Both Ways
Your mouth harbors hundreds of bacterial species, and your toothbrush picks up a share of them every time you brush. Placing that toothbrush in a dishwasher alongside plates, cups, and utensils introduces oral bacteria into the wash environment. At the same time, food particles and grease residue circulating in the dishwasher water can settle into the bristles. The dishwasher isn’t designed to sanitize objects with the bristle density and shape of a toothbrush, so neither side of this exchange works in your favor.
How to Actually Sanitize a Toothbrush
The simplest daily habit is rinsing your toothbrush thoroughly under tap water after each use, shaking off the excess, and storing it upright so it can air dry. Bacteria thrive in moisture, so a toothbrush that dries completely between uses stays much cleaner than one stored in a closed container or lying flat on a counter.
When you want a deeper clean, two methods work well:
- Hydrogen peroxide soak. Mix one teaspoon of 3% hydrogen peroxide into one cup of water. Swish the bristles in the solution or let them soak for 15 minutes, then rinse with plain water. If you soak regularly, use a fresh solution each time.
- Antibacterial mouthwash. Swish the bristles in an antibacterial mouthwash for 30 seconds. This is the fastest option and uses a product already formulated to be safe in your mouth.
Both approaches reduce bacterial counts on bristles without risking heat damage, chemical residue, or plastic breakdown. They also cost almost nothing compared to replacing a toothbrush ruined by a dishwasher cycle.
When to Just Replace the Brush
No cleaning method makes an old toothbrush as effective as a new one. The ADA recommends replacing your toothbrush every three to four months, or sooner if the bristles are visibly frayed or splayed. A worn toothbrush cleans less effectively regardless of how well you sanitize it. If you’ve been sick with something contagious, swapping in a fresh brush once you recover is a simpler and more reliable reset than trying to deep-clean the old one.