Allergy

An allergy or Type I hypersensitivity is an immune malfunction whereby a person's body is hypersensitised to react immunologically to typically nonimmunogenic substances. When a person is hypersensitised, these substances are known as allergens. The word allergy derives from the Greek words allos meaning "other" and ergon meaning "reaction" or "reactivity". Type I hypersensitivity is characterised by excessive activation of mast cells by immunoglobulin E resulting in a systemic inflammatory response that can result in symptoms as benign as a runny nose, to life-threatening anaphylactic shock and death.

Signs and symptoms

Allergy is characterised by a local or systemic inflammatory response to allergens. Local symptoms are:

Related Topics:
Inflammatory - Allergen

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• Nose: swelling of the nasal mucosa (allergic rhinitis)
• The distinctive behavior known as nasal salute, also known as allergy salute, is the habit of wiping of the nose in an upward direction due to itching.
• Eyes: redness and itching of the conjunctiva (allergic conjunctivitis)
• Airways: bronchoconstriction, wheezing and dyspnoea, sometimes outright attacks of asthma
• Skin: various rashes, such as eczema, hives (urticaria) and contact dermatitis.

Systemic allergic response is also called anaphylaxis. Depending of the rate of severity, it can cause cutaneous reactions, bronchoconstriction, edema, hypotension, coma and even death.

Related Topics:
Anaphylaxis - Cutaneous - Edema - Hypotension - Coma - Death

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Hay fever is one example of an exceedingly common minor allergy - large percentages of the population suffer from hayfever symptoms in response to airborne pollen. Asthmatics are often allergic to dust mites. Apart from ambient allergens, allergic reactions can be due to medications.

Related Topics:
Hay fever - Airborne - Pollen - Asthma - Dust mites - Allergen - Medication

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