Allergy

In this Article

• What does an allergy mean?
• What causes allergies?
• Who is at risk and why?
• What are common allergic conditions and their symptoms and signs?
• Hay Fever
• Asthma
• Allergic Eyes
• Allergic Eczema
• Hives
• Allergic Shock
• Where are allergens? Everywhere
• In the air we breathe
• In what we ingest
• Touching our skin
• Injected into our body
• Allergy At A Glance
• Pictures of Common Allergy Triggers - Slideshow
• Pictures of Pets and Allergies - Slideshow
• Pictures of Home Allegy - Slideshow
• Patient Discussions: Allergies - Describe Your Experience

Who is at risk and why?

Allergies can develop at any age, possibly even in the womb. They commonly occur in children but may give rise to symptoms for the first time in adulthood. Asthma may persist in adults while nasal allergies tend to decline in old age.

Why, you may ask, are some people "sensitive" to certain allergens while most are not? Why do allergic persons produce more IgE than those who are non-allergic? The major distinguishing factor appears to be heredity. For some time, it has been known that allergic conditions tend to cluster in families. Your own risk of developing allergies is related to your parents' allergy history. If neither parent is allergic, the chance that you will have allergies is about 15%. If one parent is allergic, your risk increases to 30% and if both are allergic, your risk is greater than 60%.

Although you may inherit the tendency to develop allergies, you may never actually have symptoms. You also do not necessarily inherit the same allergies or the same diseases as your parents. It is unclear what determines which substances will trigger a reaction in an allergic person. Additionally, which diseases might develop or how severe the symptoms might be is unknown.

Another major piece of the allergy puzzle is the environment. It is clear that you must have a genetic tendency and be exposed to an allergen in order to develop an allergy. Additionally, the more intense and repetitive the exposure to an allergen and the earlier in life it occurs, the more likely it is that an allergy will develop.

There are other important influences that may conspire to cause allergic conditions. Some of these include smoking, pollution, infection, and hormones.

What are common allergic conditions and their symptoms and signs?

The parts of the body that are prone to react to allergies include the eyes, nose, lungs, skin, and stomach. Although the various allergic diseases may appear different, they all result from an exaggerated immune response to foreign substances in sensitive people. The following brief descriptions will serve as an overview of common allergic disorders.

Allergies - Describe Your Experience

The MedicineNet physician editors ask:

Please describe your experience with allergies.

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