Allergies

Overview

Allergies are very common and they affect about 20% of the population. When the body's immune system reacts to a normal, harmless substance (like pollen, for example) by creating an antigen to fight it, that's an allergy.

Types

There are many kinds of allergies that fall within four specific groups:

• Type I: Immediate or anaphylactic reaction allergies are the types of allergies that cause an immediate reaction, typically in the mucous membranes or skin. This includes things like hay fever, food allergies, pet dander allergies and medication allergies. Any allergy that causes a fast reaction, whether it's sneezing, scratching or even a severe reaction like anaphylactic shock falls into this group. Type I allergies are the most common of all the allergies.

• Type II: These allergies are called cytotoxic, and are very rare. This type of allergy occurs when the body attacks its own damaged cells. This includes reactions to things like blood transfusions and myasthenia gravis.

• Type III: Immune complex allergies occur when something in the blood that's not usually there causes symptoms. Allergic reactions to a medication fall into this category.

• Type IV: Delayed-onset allergies occur much like Type II allergies, but with a delayed reaction. This type of allergy is also called a cellular immune reaction. When a person's body rejects a transplanted organ, or comes into contact with a substance that later shows a reaction, this is a Type IV allergy.

Symptoms

Symptoms can be mild like a rash, watery and itching eyes, sniffing and sneezing. Moderate symptoms include itching skin and difficulty in breathing. Severe symptoms in an anaphylactic reaction will usually start with itching on the face, then progress to life-threatening reactions like swelling that makes it hard to breathe or swallow, stomach pain and cramps, vomiting and diarrhea, dizziness and mental confusion.

Causes/Risk Factors

There is no way to predict who becomes allergic or why. But allergies are often hereditary and passed from parents to children. A child with one allergic parent has a 50/50 chance of being allergic and 75% of kids with two allergic parents end up with allergies.

Tests/Diagnosis

A skin test is a common way to test for allergies. A drop of the allergen is placed onto the skin and then the skin is broken with a small prick or scratch. Sometimes a small amount of the suspected allergen is injected into the skin, or the person wears a patch with the substance held against the skin for a couple of days.

There are also blood tests that can help diagnose other allergies when a skin rash is present or medication is suspected as the causes. In both cases, the patient's input and an allergy diary describing symptoms and when they occur are important in diagnosing allergies.

Treatment

Treatment depends on the type of allergy. Avoiding the cause of the allergic reaction is an important step in living with allergies.

Medications that can be used to treat allergies include:

Antihistamines: Antihistamines are available by prescription and over-the-counter. They are available in many forms such as:

• Capsules and pills
• Eye drops
• Injection
• Liquid
• Nasal spray

Corticosteroids: Anti-inflammatory medications are available in many forms such as:

• Eye drops
• Nasal spray
• Lung inhaler

Patients with severe allergic symptoms may be prescribed corticosteroid pills or injections for a short time period.