If you have ever left a baby bottle in the car on a hot day, you know the smell. It is a sour mix of old milk and regret, and a quick wash does not always make it go away.
A funky bottle is more than annoying. The odor usually means bacteria or trapped milk fat, and a baby will often flat-out refuse to drink from it.
We have scrubbed our share of stinky bottles. Below we sort the tricks that actually clear the smell from soap, sour milk, burnt plastic, bleach, and formula, plus how to stop the funk from coming back so you are not tossing perfectly good gear.
Key Takeaways
- Rinse and wash after every feeding: The CDC says to clean bottles after each use, since even a little leftover milk feeds bacteria within hours.
- Deodorize with baking soda or vinegar: A baking soda shake or a 50/50 white vinegar soak pulls sour and formula odors out of porous plastic and silicone.
- A soapy smell may be your milk, not the bottle: High lipase in stored breast milk can smell soapy or metallic; scald fresh milk before freezing to prevent it.
- Toss burnt, melted, or moldy bottles: If a bottle is warped or has mold that will not scrub out of the pores, throw it away instead of reusing it.
How Can I Prevent Bottle Odors?
Prevent bottle odors by washing baby bottles right after every feeding, taking every part off before you scrub, and letting each piece air-dry fully before it goes back in the cabinet. Milk fats cling to the sides and moisture invites bacteria, and plastic and silicone make it worse because they are porous and soak up smells.
Here is how to keep them fresh.
- Rinse and wash after every feeding: Do not let a used bottle sit. Rinse it right after the feeding, then wash it, so milk residue cannot turn sour or harden in the corners. The CDC recommends cleaning bottles after every single use (1).
- Take everything apart: Separate the nipple, ring, bottle, and any valves before washing. Milk loves to hide between the ring and the nipple base, so use a bottle brush to scrub every nook.
- Sanitize when your baby is very young: Beyond daily washing, sanitize the parts at least once a day if your baby is under 2 months old, was born prematurely, or has a weakened immune system, according to the CDC. A dishwasher run with hot water and a heated drying or sanitizing setting counts as sanitizing on its own.
- Dry completely before storing: Let every part air-dry fully before you put it away. Sealing a damp bottle in a cabinet traps moisture, and that is exactly how germs and mold get their start.
- Use the fridge in a pinch: If you cannot wash a bottle right away, rinse it and set it in the refrigerator. The cold slows bacteria growth compared with leaving it in the sink.
- Watch your storage times: The CDC says freshly expressed breast milk keeps at room temperature, 77 degrees Fahrenheit or colder, for up to 4 hours. Per the CDC, prepared formula should be used within 2 hours of mixing, and within 1 hour once your baby starts drinking. Always throw out what is left in the bottle after a feeding, since saliva mixed into formula feeds bacteria.
- Switch materials: Plastic clings to smells. If you are tired of the stink, try glass bottles. They are non-porous and much easier to keep odor-free.
How Do You Get Rid of a Specific Bottle Smell?
Match the fix to the smell: fragrance-free soap and a short boil for a soapy silicone bottle, a baking soda shake or a 50/50 white vinegar soak for sour milk and formula, a vinegar soak for burnt plastic that is not warped, and a cold water soak for bleach.
1. Bottles Smell Like Soap
This is common with silicone bottles and nipples. Oil from the soap binds to the silicone, leaving a chemical taste and smell behind.
- Switch soaps: Ditch the scented dish soap. Use a fragrance-free, free-and-clear brand, or a soap made specifically for baby products.
- Hand-wash only: Dishwashers use harsh detergents and very hot water that can degrade plastic and bake soap smells into the material.
- The vinegar rinse: After washing, rinse the bottles with hot water and a splash of white vinegar. The acid helps strip the leftover soap residue.
- Boil it out: Boil the bottles for 5 to 10 minutes in plain water. This can release the trapped soap oils from the silicone pores.
Is it the milk?
If you breastfeed, that soapy smell might actually be your milk. Some moms have high lipase activity. This enzyme breaks down the fat in milk, which can leave a soapy or metallic smell after the milk has been stored in the fridge or freezer.
If that is the case, the milk is still safe to drink, but your baby might refuse it. To prevent it going forward, scald fresh milk (heat it until tiny bubbles form around the edge) before freezing to stop the lipase activity (2).
2. Bottles Smell Like Sour Milk
If you left a bottle in the diaper bag over the weekend, you know this one. It is tough to remove, but baking soda usually does the trick.
- The baking soda shake: Wash the bottle first. Then add two tablespoons of baking soda, fill it with hot water, and shake hard for two minutes. Let it sit for four hours or overnight, then rinse.
- The vinegar bath: Vinegar cuts through fat and kills odors. Fill a clean basin with 50% hot water and 50% white vinegar, then soak the bottles and nipples for four hours or overnight. Wash them with soap and water afterward to clear the vinegar smell.
- Freeze the funk: After washing and drying the bottle, put it in the freezer empty overnight. The cold helps knock back the bacteria causing the odor.
- Check the milk source: Always smell your stored breast milk before pouring it. If the milk itself is sour, no amount of bottle cleaning will help.
3. Bottles Smell Like Burnt Plastic
This usually happens when a bottle falls onto the heating element in the dishwasher, or you forget a boiling pot on the stove.
- Inspect for damage: Look closely. Is the plastic warped, melted, or deformed? If so, throw it away. Melted plastic can leach harmful chemicals, and it is not safe to use.
- If it is just the smell: If the bottle looks perfect but picked up a burnt smell from the dishwasher air, try a vinegar soak (50/50 vinegar and warm water) overnight.
- The final test: After soaking and washing, sniff it. If it still smells like burnt chemicals, toss it. It is not worth the risk.
4. Bottles Smell Like Bleach
If you used a bleach solution to sanitize, the smell can linger.
- Cold water soak: Submerge the bottles in plain cold water for a few hours.
- Rinse and repeat: Rinse thoroughly under running water, then wash with hot, soapy water.
- Boil to finish: Boil the parts in plain water for 10 minutes to help evaporate any remaining chlorine residue.
5. Bottles Smell Like New Plastic
Fresh-out-of-the-box bottles often carry a chemical manufacturing scent.
- Baking soda soak: Dissolve four tablespoons of baking soda in a quart of hot water. Soak the new bottles and parts overnight, then wash them normally the next morning.
- Sterilize: Run them through a steam sterilizer or boil them for five minutes before the first use.
- Contact support: If a strong chemical smell hangs on after cleaning, do not use the bottles. Contact the manufacturer for a replacement.
6. Bottles Smell Like Formula
Formula takes on a distinct, cheese-like smell when it goes bad. The proteins stick stubbornly to plastic.
- Scrub with baking soda: Make a paste with baking soda and water. Use your bottle brush to work the paste into the interior walls, then let it sit for 10 minutes before rinsing.
- Charcoal trick: This one is for severe cases. Crush an activated charcoal briquette (make sure it is pure charcoal with no lighter fluid) into powder. Pour it into the bottle, fill with hot water, seal, and leave it for a few days. The charcoal absorbs organic odors. Wash thoroughly afterward.
- Replace the nipple: Often the silicone nipple holds the smell worse than the bottle. If the bottle is fine but the nipple stinks, just replace the nipple.
