Allergy

Allergy facts

• Allergy involves an exaggerated response of the immune system.
• The immune system is the body's organized defense mechanism against foreign invaders,
• particularly infections.
• Allergens are substances that are foreign to the body and can cause an allergic reaction.
• IgE is the allergy antibody.
• Allergies can develop at any age.
• Your risk of developing allergies is related to your parents' allergy history.

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 includesmoking, pollution, infection, and hormones.

What are common allergic conditions, and what are allergy 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.

Allergic Eczema

Allergic eczema (atopic dermatitis) is an allergic rash that is usually not caused by skin contact with an allergen. This condition is commonly associated with allergic rhinitis or asthma and features the following symptoms:

• Itching, redness, and or dryness of the skin
• Rash on the face, especially children
• Rash around the eyes, in the elbow creases, and behind the knees, especially in older children and adults (rash can be on the trunk of the body)

Eczema is a skin condition caused by inflammation.Atopic dermatitis is the most common of the many types of eczema. While the word "dermatitis" means inflammation of the skin, "atopic" refers to an allergic tendency, which is often inherited. These eczema sufferers have a higher risk of developing other allergic conditions (like asthma or hay fever).
Eczema is a chronic problem for many people. It is most common among infants, many of whom outgrow it before school age.

Atopic Dermatitis - This condition is the most common of all pediatric dermatoses. For the majority of patients, the onset occurs during infancy. There are symmetrical patches of erythema, exudation, and scale involving the cheeks and chin. It is not unusual also to see widespread involvement of the trunk and extensor extremities during infancy; the diaper area is most often spared.

This figure shows erythema and fissuring on the weight-bearing surface of the foot. This disorder, which tends to be worse in the winter months, is called juvenile plantar dermatitis. It is much more common in children with atopic dermatitis. Juvenile plantar dermatitis, which has also been called wet-dry foot syndrome, is caused by excessive sweating of the feet in occlusive footwear and rapid drying in a low-humidity environment. The use of emollient ointments is extremely helpful.

Allergic contact dermatitis: 

A red, itchy, weepy reaction where the skin has come into contact with a substance that the immune system recognizes as foreign, such as poison ivy, poison oak or poison sumac or certain preservatives in creams and lotions. This type of reaction reflects a specific sensitivity or allergyto a specific substance. Also called allergic contacteczema.

Nickel contact dermatitis. The development of an itchy eczematous eruption near the umbilicus is virtuallypathognomonic for contact dermatitis to nickel. The source is the small metal snap in the blue jeans or the metal belt buckle. The simultaneous occurrence of an id reaction, sometimes with small lichenoid papuleson the elbows and knees, is very common. 

Lesions can be treated effectively with topical corticosteroids, but the only cure results from strict avoidance of nickel. This is easier said than done. Parents must buy jeans without snaps or sew in a small piece of fabric to protect the underlying skin. Families should be reminded that wearing jeans with a metal snap for just several hours out of the month would reactivate the entire process. Children with contact dermatitis to nickel should also avoid metal jewelry and should be advised against ear piercing.