The 26-year-old beauty, who has a six-month-old daughter Harlow with fiance Joel Madden, is said to wash everything Harlow uses twice to ensure her child stays healthy.
A source said, "Nicole double washes her daughter Harlow's clothes and double sanitizes her bottles, baby spoons - anything Harlow eats out of."
"Even the cleaning supplies in the house have to be organic and non-toxic."
Joel is reportedly concerned Nicole has become obsessed with keeping their home spotlessly clean.
The source added to National Enquirer magazine: "Noel has always worried about germs, but Joel feels she has taken it too far. Joel wants Harlow to grow up healthy, but he thinks all this double-sterilizing is weird."
Nicole isn't the only celebrity parent to worry about their children coming into contact with microscopic nasties.
Earlier this year, it was claimed Jennifer Lopez was so terrified her twins Max and Emme would fall ill, she installed dispensers containing a special hand lotion for people to use before they enter the nursery.
She is also believed to have asked guests to put on surgical masks before they met the tots.
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