Allergies – What Is an Allergy?

There is little good news associated with hearing “you’re allergic”.

Sadly, all too many people know what an allergy is first hand. The itchy eyes, runny nose, skin rash and other symptoms are uncomfortably familiar. But a more accurate medical definition can be helpful, because it’s the first step toward diagnosis and treatment for the right condition.

The definition of allergy derives from a large body of facts. It is a hypersensitive reaction to allergens that produce an allergic reaction. But that definition is circular. What is an allergen? What’s an allergic reaction? Let’s flesh it out.

In a percentage of the population, exposure to otherwise harmless substances called allergens causes a type of white blood cells to produce a biochemical called IgE (Immunoglobulin E). Inside the body, that compound then attaches to mast cells or basophils (more white blood cells). They in turn release histamines, prostaglandins and other compounds. Their overproduction are what create the actual symptoms you feel.

The results of all that activity for an individual vary. The strength and type of reactions will differ from person to person. Some will experience mild to severe asthma. Others develop a skin rash, such as eczema. Still more suffer from the common watery eyes and running nose. Hives, hay fever and even anaphylaxis may occur.

So, an allergen is any substance that will cause a person to experience these allergic reactions. That covers a lot of ground, regrettably.

Such well known environmental entities as pollen affect millions. Many are sensitive to animal dander and dust mites. Some people are allergic to bee or wasp stings. Still others experience symptoms when they come into contact with or consume certain foods, such as milk, peanuts or shellfish.

There is a significant genetic component to being affected, a condition called atopy. But, allergies can be built up over time with repeated or prolonged exposure.

A small amount of dust, for example, may leave an otherwise sensitive person unaffected. But, over time, as more dust mites carried on the particles enter the nasal cavities and sit in the sinuses, they release more and more material. The eventual result can be the familiar rhinitis or runny nose associated with that particular allergy.

Similarly, conjunctivitis (a swelling and irritation of the membranes lining the eyelid) are a common result of exposure to some environmental substances. It is a typical symptom of hay fever, hives and other allergic reactions that are uncomfortable but rarely dangerous.

Still more serious reactions are not only possible, but almost guaranteed in some cases. Certain people are hypersensitive to bee stings. One sting can produce anaphylactic shock, a reaction that can lead to severe respiratory distress, circulatory system difficulty or even death. Onset can be rapid and include drastically lower blood pressure, constricted breathing and severe skin rashes. Fortunately it’s easily treated with epinephrine or cortisone.

Testing for allergies, and treating them, has improved in the past few decades. Though procedures may still be unpleasant and treatments less than perfect, advances have allowed the allergy sufferer to find relief quickly. Cures are few and far between, but symptom relief can be substantial and long lasting.

For millions, that’s good news.


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