What causes allergies?
The causes of allergies are not fully understood. Children get allergies from coming into contact with allergens. Allergens can be inhaled, eaten, injected (from stings or medicine), or they can come into contact with the skin. Some of the more common allergens are:
- Pollens
- Molds
- House dust mites
- Animal dander and saliva (cat, dog, horse, rabbit)
- Chemicals used in industry
- Some foods and medicines
- Venom from insect stings
The tendency to have allergies is often passed on in families. For example, if a parent has an allergy problem, there is a higher than normal chance that his or her child also will have allergies. This risk increases if both parents are allergic.
The following are some common allergies, their triggers, and their symptoms.
Common Allergies
Asthma
- Triggers
A wide range of things can trigger an asthma attack. These include cigarette smoke, viral infections, pollen, dust mites, furry animals, cold air, changing weather conditions, exercise, and even stress.
- Conditions
Coughing, wheezing, difficult breathing; coughing with activity or exertion; chest tightness.
Hay Fever
- Triggers
Pollen from trees, grasses, or weeds.
- Conditions
Stuffy nose, sneezing, and a runny nose; breathing through the mouth because of stuffy nose; rubbing or wrinkling the nose and facial grimacing to relieve nasal itch; watery, itchy eyes; redness or swelling in and under the eyes.
Food Allergies
- Triggers
Any foods, but the most common are eggs, peanuts, milk (see information on milk allergies), nuts, soy, fish, wheat, peas, and shellfish.
- Conditions
Vomiting, diarrhea, hives, eczema, difficult breathing, and possibly a drop in blood pressure (shock).
Eczema (atopic dermatitis)
- Triggers
Sometimes made worse by food allergies, contact with allergens (pollen, dust mites, furry animals), irritants, sweating.
- Conditions
A patchy, dry, red, itchy rash that often occurs in the creases of the arms, legs, and neck; however, in infants it often starts on the cheeks, behind the ears, and on the thighs.
Hives
- Triggers
Viral infections, food allergies, and drugs (such as aspirin, penicillin, or sulfa) but cause is often unknown.
- Conditions
Itchy, mosquito-bite-like skin patches that are more red or pale than the surrounding skin. Hives may be found on different parts of the body and do not stay at the same spot for more than a few hours.
Contact Dermatitis
- Triggers
Contact with a plant substance such as poison ivy or oak, household detergents and cleansers, and chemicals in some cosmetics and perfumes.
- Conditions
Itchy, red, raised patches that may blister if severe. Most of these patches are confined to the areas of direct contact with the allergen.
