I wash the baby bottles by hand and often let them air dry. Do I have to dry them completely before adding breast milk? I would obviously want to get all of the dish liquid out of the bottles. But I wasn't sure if the breast milk mixing with a small amount of water would have any impact on the baby. I would think that he might just pee slightly more frequently if I don’t dry them fully?

I'm using Dr. Brown's bottles, so drops of water collect on the nipple, bottle, vent, vent cap, and cap.

It's not clear if these trace amounts of water would contribute to water intoxication.

My child is 3 months old.

  • Water itself isn't dangerous because as water is mixed with formula our breastmilk is mostly comprised of water. It's TOO much water that's dangerous. Commented May 13, 2015 at 12:32

2 Answers 2


Breast milk is, essentially, water with a bunch of other nutritious stuff in it.

Water intoxication can be a concern if an infant drinks too much plain water in addition to breast milk or formula, but that requires a significant volume of water:

Breast milk or formula provides all the fluid healthy babies need. If a mother feels her baby needs to take additional water, it should be limited to two to three ounces at a time and should be offered only after the baby has satisfied his hunger with breast feeding or formula.

A few drops of water is much less than the two to three ounces (about 1/4 to 1/3 cup) limit. So any very small amount of water remaining in the bottle after it's washed and left to air dry is not a danger. I doubt it would even be enough to make a noticeable difference in how much he pees.

  • Good to have a number on how much addtl. water is safe!
    – Stephie
    Commented May 13, 2015 at 12:44

The water content of breast milk varies a lot (even during feedings) - much more than a few drops of remaining water would "dillute".

Please take a look at this picture from wikipedia: thinner (=more watery) foremilk vs. thicker (=fattier) hindmilk.

Fore and hindmilk

The only reason to be worried would be if you were washing the bottles with unsafe water, for example if you were in a country where drinking tap water or eating washed but uncooked fruit is considered unsafe for us "westerners". But in this case, simply letting the bottles dry wouldn't suffice, you'd have to "sterilize" them.

  • Wow, I've never actually seen them separated like that before :D
    – Acire
    Commented May 13, 2015 at 12:37
  • @Erica: Usually you don't but there are two scenarios how you might see this: A) pumping just a tiny bit to reduce pressure if the supply is too high, B) pumping after baby has fed to increase supply.
    – Stephie
    Commented May 13, 2015 at 12:53

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