What Causes Allergic Reactions?

An allergen is any substance that produces an allergic reaction. But that sounds circular. To flesh it out a little simple science is all that's needed.

The body's immune system releases antibodies to anything it views as a foreign substance. Bacteria, viruses and even transplanted organs have a genetic 'signature' that doesn't match that of an individual. So, they're seen as something foreign, something the body needs to eliminate.

To do that, white blood cells move to an area where the foreign substance is located. In the case of an allergen, those are usually proteins such as pollen or those found in certain foods like milk or peanuts. The white blood cells then cause the release of histamines and enzymes into the surrounding fluid to envelop the foreign protein.

But there enters the second factor in an allergic reaction: you.

For reasons not fully clear but having a known genetic factor, the immune system of some individuals overreacts. It produces too much for too long of these allergen fighting substances. The result is the familiar watery eyes, itchy skin, runny nose and other allergy symptoms.

That sensitivity isn't necessarily a fixed amount, either. Repeated exposure over a period of time can cause a 'ramp up' to an allergic reaction. As an example, consider an allergic reaction to dust.

We inhale dust all the time. Some people can do this for a lifetime and never produce anything more than an ordinary sneeze. The body filters out the material and all goes on as normal. But, the dust also carries dust mites, who shed proteins in their waste. Over time, some people will gradually generate an overly strong immune system reaction to those proteins.

The underlying genetic factor has not been precisely identified. But, statistically, it is known that allergies tend to run in families. Still, there are environmental factors - beyond the mere presence or absence of allergens - that play a role as well.

For example, breast fed babies tend to have fewer allergies, even within families known to be at greater risk. For the first few weeks after birth, the baby's immune system is not yet fully developed. Mothers aid in that process by delivering antibodies during feeding that the child doesn't yet create on its own.

It might appear at first blush that stomach acid would destroy the helpful antibody proteins given in breast milk and colostrum. But, unlike adults, babies produce much less stomach acid. So, a percentage of the prolactin and other helpful compounds survive the infant's digestive process. The process is also helped by the fact that immuno-proteins are glycosylated, a kind of wrapper that helps protect them from being broken down in the child's stomach.

The full details of allergic reactions are still a matter of ongoing research. But, there are many things a person can do to minimize his or her risks. Before showing how, we need to know a little bit more about how the immune system works...