Health

food sensitivities like the infant in the OP, but that's not the same as a food allergy.

Allergies are an immune system overreaction to non-threatening substances - or, to substances that most people do not react to. The allergic person's immune system is unable to distinguish between harmless substances and harmful microbes like bacteria, viruses, fungi. It's an inbuilt biological malfunction issue that they are born with. An allergy develops when they come in contact with something that triggers the immune system's inborn malfunction.

Several parts of the body are involved in immune responses, creating a number of possibilities for malfunctioning immune reactions. Allergies can involve hormones like adrenalin production in the adrenal glands (on top of the kidneys), T cells, macrophages, immunoglobulins (especially IGA and IGE), plus the lymph system and immune cells in the skin.

Specific allergies are not inherited, but immune system problems that cause allergies to develop are heritable, which is why being allergic often runs in families. Sometimes the person's immune system turns on its own body causing autoimmune disorders, literally becoming allergic to oneself, or to one or more of the body's own parts.

I was born with immunological functioning issues (the capacity to develop allergies) which manifested shortly after birth in an allergy to cow's milk formula. I am NOT lactose intolerant, which is different from a milk allergy. I also no longer react to cow's milk, fortunately.

As a child, I played in dirt constantly. My father had half our yard planted in vegetables and half in lawn, shrubs, and flowers, so I was exposed to all kinds of pollen, too. In the fall, he uprooted harvested plants, turned over the soil, and let us play in it.

We washed before meals, of course, but did not have antibiotic soaps and the numerous sanitizing products that exist today. But, in spite of all those "dirt" exposures, I developed more and more allergies as I grew. I spent my entire childhood being chronically congested due to living with things that I now know are allergens for me, but which were not diagnosed by doctors in my childhood - a feather pillow, a wool blanket, a real pine tree at Christmas, etc.

I have skin contact allergies, pollen allergies, medicine allergies, and food allergies. So did my mother, although not always to the same substances. My siblings all developed allergies later in life. As often happens in people with multiple allergies, I also developed an autoimmune disorder in later life. So did my mother and sister.

Rant over. I just get frustrated with the lack of understanding about allergies among many people, even doctors. I had to learn about them but wish that I hadn't needed to.