ALLERGOLOGY The branch of medical science that studies the causes and treatment of allergies

Allergy a disorder of the immune system often also referred to as atopy occur to normally harmless environmental substances known as allergens

allergy is one of four forms of hypersensitivity and is called type I (or immediate) hypersensitivity characterized by excessive activation of certain white blood cells called mast cells and basophils by a type of antibody known as IgE, resulting in an extreme inflammatory response

What is hypersensitivity? Abnormal sensitivity, a condition in which there is an exaggerated response by the body to the stimulus of a foreign agent. example: allergy

Comparison of hypersensitivity types TypeAlternative names Often mentioned disordersMediators IAllergy (immediate) Atopy IgE Anaphylaxis Asthma II Cytotoxic, antibody- dependent Autoimmune hemolytic anemiaIgM or IgG Thrombocytopenia(Complement) Erythroblastosis fetalis Goodpasture's syndrome III Immune complex disease Serum sicknessIgG Arthus reaction(Complement) Systemic lupus erythematosus (SLE) IV Delayed-type hypersensitivity (DTH), cell-mediated immune memory response, antibody-independent Contact dermatitis T-cells Mantoux test Chronic transplant rejection Multiple sclerosis VAutoimmune disease Grave's diseaseIgM or IgG Myasthenia Gravis(Complement) Hashimoto's thyroiditis Systemic lupus erythematosus

Common Allergic Reaction Hives hay fever Asthma Food allergies Reactions to the venom of stinging insects such as wasps and bees

Affected OrganSymptom Nose Swelling of the nasal mucosa (allergic rhinitis) Sinuses allergic sinusitis Eyes redness and itching of the conjunctiva (allergic conjunctivitis) Airways sneezing, coughing, and sometimes outright attacks of asthma Ears feeling of fullness, possibly pain, and impaired hearing due to the lack of eustachian tube drainage Skin rashes, such as hives (urticaria) Gastrointestinal tract abdominal pain, vomiting and diarrhea

Cause Risk factors for allergy can be placed in two general categories, namely host and environmental factors. Host factor: –heredity, sex, race, and age Environmental factor: – alterations in exposure to infectious diseases during early childhood, environmental pollution, allergen levels, and dietary changes –Aside from these ambient allergens, allergic reactions can result from foods, insect stings, and reactions to medications like aspirin and antibiotics such as penicillin.

Treatment Pharmacotherapy –several antagonistic drugs are used to block the action of allergic mediators, or to prevent activation of cells and degranulation processes. These drugs help to alleviate the symptoms of allergy, and are imperative in the recovery of acute anaphylaxis, but play little role in chronic treatment of allergic disorders. Immunotherapy –Desensitization or hyposensitization is a treatment in which the patient is gradually vaccinated.