Allergies occur when the immune system mistakenly identifies a harmless substance as a potentially harmful invader and triggers a systemic reaction to rid the body of the substance. Symptoms of allergies can involve the skin, sinuses, respiratory tract and digestive system, according to MayoClinic.com. The severity of allergic reactions also varies between individuals. Some people experience minor irritation, while others suffer from a life-threatening reaction.
Common Allergens
There are a number of substances that commonly illicit allergic reactions in a number of people. These substances are referred to as allergens. Common airborne allergens include pollen, dust, mold and animal dander, according to the American Academy of Family Physicians. Food is another common substance that may trigger an allergic reaction. Common food allergens include peanuts, tree nuts, shellfish, eggs, milk, wheat and soy. Insect stings, such as from a bee, can trigger an allergic response as well. Some people are allergic to specific medications, such as penicillin.
Physiology of an Allergic Reaction
The immune system produces proteins called IgE antibodies that are responsible for identifying harmful substances and attacking them. When an allergen enters the body, the IgE antibodies react abnormally and interpret the allergen as a potentially harmful invader. This causes the release of histamines, which are compounds that trigger an inflammatory response in the body. Histamines attach to histamine receptors in body cells and cause the cells to swell and release fluid, which causes the symptoms associated with an allergic response.
Angioedema
Although symptoms of allergies vary depending on which area of the body is affected and the type of allergen causing the allergic response, a common general reaction is a systemic body inflammation referred to as angioedema. Angioedema is an inflammation of the body that occurs just under the skin surface. Angioedema most commonly affects the eyes and lips, but can also appear on the hands, feet, genitals and throat, according to MayoClinic.com.
Symptoms
Specific symptoms are dependent on the types of allergens. If the allergen enters the respiratory tract, it can cause congestion, runny nose and watery, swollen eyes. An allergen that comes into contact with the skin causes itchiness, redness, inflammation and flaking skin. Food allergies can cause tingling in the mouth, inflammation of the lips, tongue, face or throat and hives. Allergies to insect stings often result in inflammation at the area of the sting, itching, hives, cough, chest tightness and shortness of breath.
Treatment
Minor allergic reactions can usually be successfully treated with over-the-counter antihistamines, which block histamine receptors in the body and prevent the systemic body inflammation and resulting symptoms. Corticosteroids may also be helpful to reduce inflammation. Severe allergic reactions, known as anaphylaxis, require an emergency injection of epinephrine, which can reduce inflammation and swelling of airways immediately.
