What Causes Allergies?

The substances that cause allergic disease in people are known as allergens. "Antigens," or protein particles like pollen, food or dander enter our bodies through a variety of ways. If the antigen causes an allergic reaction, that particle is considered an "allergen." These can be:

Inhaled
Plant pollens that are carried by the wind cause most allergies of the nose, eyes and lungs. These plants (including certain weeds, trees and grasses) are natural pollutants produced at various times of the year when their small, inconspicuous flowers discharge literally billions of pollen particles.

Unlike wind-pollinated plants, conspicuous wild flowers or flowers grown in most residential gardens are pollinated by bees, wasps, and other insects and therefore are not widely capable of producing allergic rhinitis.

Another culprit: house dust that can include dust mite particles, mold spores, cat and dog dander.

Ingested
Frequent culprits include shrimp, peanuts and other nuts.

Injected
Such as medications delivered by needle like penicillin or other injectable drugs; venom from insect stings and bites.

Absorbed
Plants such as poison ivy, sumac and oak and latex are examples.

Genetics
Like baldness, height and eye color, the capacity to become allergic is an inherited characteristic. But that doesn't make you automatically allergic to specific allergens. Several factors must be present:

• Specific genes acquired from parents.
• Exposure to one or more allergens to which you have a genetically programmed response.
• Degree and length of exposure.

A baby born with the tendency to become allergic to cow's milk, for example, may show allergic symptoms several months after birth. A genetic capability to become allergic to cat dander may take three to four years of cat exposure before the person shows symptoms.

On the other hand, poison ivy allergy (contact dermatitis) is an example of an allergy in which hereditary background does not play a part. Substances other than plants, such as dyes, metals, and chemicals in deodorants and cosmetics, can also cause a similar dermatitis.