Safe Formula Milk Temperature for Infants: Avoiding Bacterial Infections

The temperature of formula milk foam?

Hello Doctor, my baby is 4 months old and currently on formula milk.
On August 7th, while we were out, I prepared freshly boiled water and stored it in a thermos.
About four hours later, I took it out to mix the formula, and the temperature felt lower than the usual 70 degrees Celsius, but I let my baby drink it at that time.
Later, I borrowed water twice at a friend's house to feed the baby, but I found out that the temperature was only 55 degrees Celsius.
Since there were three meals with this situation, I am a bit worried about potential bacterial infections.
Currently, my baby does not have any symptoms of diarrhea or vomiting.
Should I be concerned about infections such as Salmonella, Listeria, or Enterobacter sakazakii? Given that Listeria has a longer incubation period, are there specific symptoms I should monitor in my baby? Thank you, Doctor!

Xinshou Ma, 20~29 year old female. Ask Date: 2021/08/08

Dr. Xiao Kaiwen reply Pediatrics

If I want to prepare formula milk with water that has already been boiled, in principle, there should be no pathogenic bacteria present.
Even if the water has been left to cool for a while, the likelihood of pathogenic bacteria developing should be low, especially since it is consumed only occasionally.
Therefore, I believe the risk of developing an illness is minimal and there is no need to worry excessively.
Symptoms of ingesting pathogenic bacteria typically include gastrointestinal symptoms such as vomiting, diarrhea, and fever.

Reply Date: 2021/08/08

More Info

When it comes to preparing formula milk for infants, ensuring the right temperature is crucial for both safety and nutrition. In your case, you mentioned that the water used for mixing the formula was initially boiled and then stored in a thermos for about four hours. After this period, the temperature of the water was lower than the typical 70 degrees Celsius (158 degrees Fahrenheit) that is often recommended for preparing formula. You also noted that subsequent feedings were done with water at around 55 degrees Celsius (131 degrees Fahrenheit).
First and foremost, it is important to understand that boiling water is effective in killing most bacteria, including pathogens like Salmonella, Listeria, and Enterobacter sakazakii, which can be particularly concerning for infants. However, once the water cools down, the risk of bacterial growth can increase, especially if it is stored for an extended period or not kept at a safe temperature.
The general guideline for preparing formula is to use water that is at least 70 degrees Celsius. This temperature is sufficient to kill any bacteria that may be present in the formula powder itself. When water is cooled to 55 degrees Celsius, while it is still warm, it may not be hot enough to ensure that any potential bacteria in the formula are effectively killed.
In your situation, since your baby is currently healthy and showing no symptoms of gastrointestinal distress such as diarrhea or vomiting, the risk of infection from the formula prepared with water at lower temperatures is likely minimal. However, it is always wise to monitor for any signs of illness. Symptoms to watch for include:
1. Diarrhea: Frequent loose or watery stools can indicate an infection.

2. Vomiting: Any episodes of vomiting should be noted, especially if they are persistent.

3. Fever: A temperature above 38 degrees Celsius (100.4 degrees Fahrenheit) can be a sign of infection.

4. Irritability or lethargy: If your baby seems unusually fussy or less active than normal, this could be a cause for concern.

Regarding Listeria, it is known for having a longer incubation period, which can range from a few days to several weeks. Therefore, if you notice any of the above symptoms in the coming days or weeks, it would be prudent to consult your pediatrician.

To minimize the risk of bacterial infections in the future, consider the following tips:
- Always use freshly boiled water: If you need to prepare formula while out, try to ensure that the water remains at a safe temperature or use a portable bottle warmer.

- Avoid prolonged storage: If water is prepared in advance, it should ideally be used within two hours if kept at room temperature, or within 24 hours if refrigerated.

- Check the formula: Always inspect the formula for any signs of spoilage or contamination before use.

In conclusion, while the risk of bacterial infection from the formula prepared at lower temperatures seems low given your baby's current health, it is essential to remain vigilant and follow safe preparation practices to ensure your baby's health and safety. If you have any further concerns or if your baby shows any symptoms, do not hesitate to reach out to your healthcare provider for advice.

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