ALLERGIES

What does an allergy mean?• An allergy refers to an exaggerated reaction

by our immune system in response to bodily contact with certain foreign substances.

• It is exaggerated because these foreign substances are usually seen by the body as harmless and no response occurs in non- allergic people.

• Immune responses are primarily mediated by a variety of white blood cell sub-types.

What does an allergy mean?

• An allergy is also called hypersensitivity.• Allergies are triggered by antigens (any foreign

molecule that stimulates an immune response) called allergens.

• The resulting immune response is what causes inflammation and damages the body, not the allergen itself.

Major Types of Hypersensitivity

1. Delayed Hypersensitivity – Mediated by helper T cells and macrophages; independent of antibodies.

2. Immune-complex Hypersensitivity – Mediated by antigen-antibody complexes deposited in tissue.

3. Immediate Hypersensitivity – Mediated by IgE antibodies, mast cells, and eosinophils.

Definition of Terms• B Cell – Cells that when activated secrete antibodies.• Immunoglobulin (Ig) – Proteins that function as B-Cell

receptors and antibodies.• Antibodies – Immunoglobulins secreted by plasma cells. • Helper T Cells – Class of T cells that activate B cells.• Cytokines – Protein messengers that regulate immune

responses.• Macrophages – Cells that function as phagocytes.• IgE – Class of antibodies that mediate immediate

hypersensitivity.• Histamine – An inflammatory mediator secreted by mast cells• Mast Cells – Tissue cell that IgE binds to in order to release

inflammatory mediators

Delayed Hypersensitivity

• Inflammatory response is independent of antibodies.

• Caused by increased secretions of cytokines by helper T cells activated by antigens in the area.

• Cytokines act as inflammatory mediators and activate additional mediators.

• Takes several days to develop.– Ex: Poison Ivy rash

Delayed Hypersensitivity

Immune-Complex Hypersensitivity

• Antibodies combine with free antigens.• These complexes precipitate out of the surface

of endothelial cells or are trapped in the walls of capillaries.

• The inflammatory immune response induced damages the tissues immediately surrounding the complexes.– Ex: Allergy to penicillin.

Immune-Complex Hypersensitivity

Immediate Hypersensitivity

• Also called IgE-mediated hypersensitivity.• Initial exposure to the antigen leads to some

antibody synthesis and production of memory B cells that activate immunity.

• When exposed to the antigen again, it elicits a more powerful antibody response.

• Particular antigens can stimulate the production of IgE antibodies.

• IgE antibody production leads to the release of inflammatory mediators such as histamine.

Immediate Hypersensitivity

Immediate Hypersensitivity

• Symptoms of IgE-mediated allergy:– Increased mucus secretion– Increased blood flow– Swelling of the epithelial lining– Contraction of smooth muscle surrounding

airways

A severe reaction can lead to anaphylaxis, which is death due to circulatory and respiratory failure.

ALLERGY TREATMENT

While there is no cure for allergies, they can be managed effectively by a combination of three treatment modalities: • Allergen avoidance• Immunotherapy • Allergy Medications

• Allergy diagnosis is the first step

allergy testing can let you know for certain which allergens are affecting you. Testing may reveal allergens that you didn't even realize were causing you problems. It is important to identify and confirm allergens that trigger your symptoms.

Allergen Avoidance

Animal allergies• allergy to animal dander, hair, and saliva is

a common problem with household pets. Pets that causing allergies include dogs, cats and birds

• The best avoidance measure for a pet allergy is removing the animal from the house completely if you so emotional and cant do that, and keep it off of furniture and bedroom as much as possible.

• Have someone else bathe the pet• Vacuum the carpet and floors frequently

Dust mites • Dust mites are microscopic creatures that

live in our bedding, pillows and mattresses and eat human dead skin flakes. Many people can be allergic to dust mite

• Avoidance of dust mites includes frequent washing of bedding, in hot water every week.

• Other bedding materials such as blankets and comforters should be washed once to twice a month. Decorative pillows and stuffed animals also harbor dust mites, and should be washed frequently or removed from the bed

When you get allergy shots (immunotherapy), your allergist or doctor injects small doses of substances that you are allergic to under your skin.

This helps your body "get used to" the allergen, which can result in fewer or less severe symptoms of allergic rhinitis.

Immunotherapy: allergy shots

Immunotherapy Facts

• Helps people with severeallergies or people who haveallergy symptoms over threemonths a year.• Works best for airborneallergies and insect stingallergies.• Doesn’t work well for foodallergies or hives.• Helps protect children withallergies from developingasthma.

Allergy Medications• In general there is no cure

for allergies, but there are several types of medications available both over the counter and prescription to help treat annoying symptoms like congestion and runny nose.

• Allergy medications are available as pills, liquids, inhalers, nasal sprays, eye drops, skin creams

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Vander, Arthur J., James H. Sherman, and Dorothy S. Luciano. Human Physiology: The Mechanisms of Body Function. Boston: McGraw-Hill, 2001. Print.