The immune system is known to be functionally asymmetrical, and immune hypersensitivity is higher on the left side of the body. It’s possible that enhanced immunosensitivity has an effect on tissue- plumping growth hormones such as estrogen. The immune system may send to the brain information that is asymmetrically expressed. Immune system asymmetry may also explain why cancers occur 5-10 percent more often in the left breast and inflammation associated with herpes zoster affects the left side more than the right. * Nursing infants may make the left breast even larger. Although studies have not found a link between a larger left breast and handedness, many women report that they prefer having their dominant right hand free while breastfeeding, which means infants more often nurse on the left breast. Favoring the left breast makes it larger. Personally, I prefer the reply my friend gave her curious 8-year-old girl when she saw that Mom’s left boob was bigger: It’s because I have a really big heart under it.
Source: Tuorimuo Elvis Philip/Upper West Media/Ghana.