Allergy is an exaggerated immune response or reaction to substances that are generally not harmful. Allergy is caused by a highly sensitive immune system which leads to a misguided immune response. Normally, the immune system protects the body from harmful substances such as bacteria and viruses. An allergic reaction occurs when the immune system reacts to substances (allergens) that are usually harmless to which most people do not produce an immune response.
In a child with allergies, first exposure to an allergen stimulates the immune system to recognize the substance. Any subsequent exposure to allergens typically causes symptoms. When an allergen enters the body of a person who has the sensitized immune system, certain cells release histamine and other chemicals. This causes itching, swelling, mucus production, muscle spasms, hives, skin rash and other symptoms.
Allergies in Children — Symptoms
Symptoms vary in severity from one person to another. Most people have symptoms that not only cause the discomfort but also endanger their lives, while a few people have life-threatening reactions (called anaphylaxis).
The body part that comes into direct contact with the allergen influences the symptoms. For example, normally, inhaled allergens cause nasal congestion, itching in nose and throat, mucus production, coughing or wheezing. In general, food allergies can cause abdominal pain, cramping, diarrhea, nausea, vomiting or other severe life-threatening reactions. Often, any allergy to plants normally produces a rash and an allergic reaction to medications affects the whole body.
Allergy symptoms vary depending on what is causing the reaction and in which part of the body it occurs. Symptoms may include:
Increased tears, runny nose, burning or itching sensation in the eyes red eyes, conjunctivitis, edema of the eyes Itching in the nose, mouth, throat, skin or any other area, whistling cough difficulty breathing, Urticaria (hives on the skin) eruption, colic skin, headache, vomiting and diarrhea.
Some diseases are related to allergies such as eczema and asthma, among many others.
Common allergens include environmental agents that have contact with the skin, airways or on the surface of the eye (such as pollen, dander and dust). Similarly, allergic reactions can be caused by insect bites, jewelry, cosmetics, and almost any substance that has contact with the body.
Some people have a kind of allergic reaction to cold or warm temperatures, sun or other physical stimuli, and some friction (rubbing or blows to the skin) symptoms. Allergies are relatively common and it has been found that factors such as heredity and environmental conditions play a role in allergies.