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What causes hay fever?

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If you suffer from hay fever (allergic rhinitis), it's because your immune system views harmless inhaled pollen or other allergens as dangerous substances invading the body. Your system overreacts, flooding your bloodstream with chemicals like histamine and leukotrienes, which inflame the lining of your nasal passages, sinuses, and eyelids. This sets in motion other symptoms associated with hay fever, such as sneezing.

All of these symptoms are meant to protect your body either by trapping and expelling the allergen or by swelling body areas, such as the nasal passages, so the allergen can't enter. Because of congestion in the veins in the lining of your sinuses, dark circles -- commonly known as allergic shiners -- may appear under your eyes. If you have perennial allergic rhinitis, they may be present all year round. The swelling of your nasal membranes may also close the sinus drainage openings, causing sinusitis. Rhinitis may also be associated with nasal polyps -- small, non-cancerous growths. You can also get nosebleeds.

From: Understanding Hay Fever -- the Basics WebMD Medical Reference

Reviewed by Neha Pathak on February 16, 2017

Medically Reviewed on 2/16/2017

SOURCES: 

News release, Sanofi-aventis U.S. 

Golightly L. . 2005. Drugs

Taramarcaz P. , December, 2004.  Clinical and Experimental Allergy

laiss M. , November 2004.  Clinical Therapy

Berger W. 2004.  Paediatric Drugs,

Huggins, J. , August 15, 2004.  American Family Physician

Bousquet J. , 2004.  Allergy

Incaudo, G. , October 2004.  Clinical Review of Allergy Immunology

Wilsom, A. , March 1, 2004.   American Journal of Medicine

MedlinePlus Medical Encyclopedia: “Hay Fever.” 

MedlinePlus Medical Encyclopedia: "Allergy."

Reviewed by Neha Pathak on February 16, 2017

SOURCES: 

News release, Sanofi-aventis U.S. 

Golightly L. . 2005. Drugs

Taramarcaz P. , December, 2004.  Clinical and Experimental Allergy

laiss M. , November 2004.  Clinical Therapy

Berger W. 2004.  Paediatric Drugs,

Huggins, J. , August 15, 2004.  American Family Physician

Bousquet J. , 2004.  Allergy

Incaudo, G. , October 2004.  Clinical Review of Allergy Immunology

Wilsom, A. , March 1, 2004.   American Journal of Medicine

MedlinePlus Medical Encyclopedia: “Hay Fever.” 

MedlinePlus Medical Encyclopedia: "Allergy."

Reviewed by Neha Pathak on February 16, 2017

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Who is most likely to get hay fever?

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