"I breast-fed Bobby until he was 6-months-old and when we made the transistion from breast milk to formula we noticed this awful change in him", Jennifer revealed.
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She continued: "The symptoms weren't getting any better and it was distressing to the whole family as they could see how it was affecting mine and my husband's relationship."
Jennifer gave birth to Bobby in 2010, but has waited until now to talk about her son's allergies - an allergy which can affect between 2 to 7.5 per cent of children under the age of one.
She added: "We were given a specialised formula which we had to go and get from the chemist. We noticed an instant change. It was like we had our old baby back, he became so happy, so content.
"It was joy to our relationship, to being a mum, and to Bobby."
Jennifer's second son Harry also suffered from CMA and in September 2014 the former Brookside actress revealed that she had given birth to a third little boy, named Charlie.
Speaking in 2013, Jennifer revealed that she suffered from post-natal depression following the birth of Bobby, and that she was worried about it returning with her other children.
"There was a kind of baby blues that never went away," the mum-of-three explained to Daybreak's Lorraine Kelly and Aled Jones.
"I was really terrified because it just doesn't affect me and the baby, it affects the whole family. And also I had my little boy… Having a new brother or sister is a big enough change for him, so for his mum going through depression as well, that was just terrifying to think of."