An allergy is the result of the immune system overreacting to a substance that is typically harmless, such as plant pollen or animal dander. This overreaction causes the release of chemicals, including histamine into the bloodstream and may result in runny nose, sneezing, itching, nasal congestion and cough.
Having a family history of allergies seems to be the main reason that people develop allergies. If both parents have allergies, their child has a 75% chance of being allergic. If only one parent has allergies, their child has a 30–40% chance of developing some form of allergy. If neither parent has allergies, a child still has a 15% chance of developing allergies. Although children are more likely to develop allergies, anyone may develop an allergy at any age. Approximately 50 million people in the United States suffer from allergies; of these, at least 9 million have asthma.
With the use of skin testing, specific allergens can be identified. For the testing, a small amount of diluted extract containing pollen, animal dander, mold, etc is placed on the skin, followed by a light puncture or scratch. Within 15 minutes, a positive reaction (similar to a mosquito bite) may appear. This information can be used to develop a specific treatment plan including avoidance measures, medication and possibly allergy shots.