Annie Ferguson Muscato, from Gainesville, Florida, was out at a Target shop on Sunday afternoon buying hypoallergenic powder formula for her two-month-old daughter Ellie Jo.
As she was buying the can of formula another shopper approached her and said 'breast is best'.
The incident angered the mother-of-one so much that she took to Facebook to share a post explaining the circumstances around her decision not to breastfeed her newborn.
Annie starts the post by revealing how she and her husband Derek had been so excited at the prospect of breastfeeding their first child – attending the four-hour breastfeeding class together and seeing a special lactation consultant.
Within an hour of Ellie Jo being delivered at the hospital the breastfeeding plan had begun as 'it was important' for Annie.
However, it was not meant to be and after the new family returned home, Ellie Jo began exhibiting signs of distress after feeding.
Annie said; 'I know that my baby began screaming after she ate. Writhing in pain. Inconsolable. I know over the last month and a half I have exclusively pumped and tried slow flow bottles of breast milk, I have tried different positions, I have seen another lactation consultant.
'I know I have held my child, my baby, while she screamed for hours- one day for eight hours straight.'
After advice from her pediatrician, the new mum even cut out soy, dairy and leafy greens from her diet to make the milk easier to digest.
But nothing would work.
The new mum eventually decided to make the switch to hypoallergenic dairy protein-free formula, under medical advice.
Ellie Jo responded well to the change in diet; 'She started smiling. She started interacting. She started sleeping.
'I thought my body failed her. I thought she wouldn't be as healthy on formula. I know you think I must not care or I'm lazy, or maybe you were genuinely trying to be helpful and thought no one had ever told me the benefits of breast feeding.'
The post, which has now been shared over 23,000 times and received nearly 3000 comments, ends by reminding mums to support each other in their decisions.
Annie said; 'What I know that you don't is that breast ISN'T always best. I know happy, healthy baby is best. I know FED is best. What I'm sure we both know is that parenting is hard. Really hard. That sometimes what we plan for and what we want just doesn't work out, but we are all here trying to do what's best for our babies.'