Allergy

Also called: Hypersensitivity

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Summary

An allergy is a reaction by your immune system to something that does not bother most other people. People who have allergies often are sensitive to more than one thing. Substances that often cause reactions are:

Pollen
Dust mites
Mold spores
Pet dander
Food
Insect stings
Medicines

Normally, your immune system fights germs. It is your body's defense system. In most allergic reactions, however, it is responding to a false alarm. Genes and the environment probably both play a role.

Allergies can cause a variety of symptoms such as a runny nose, sneezing, itching, rashes, swelling, or asthma. Allergies can range from minor to severe. Anaphylaxis is a severe reaction that can be life-threatening. Doctors use skin and blood tests to diagnose allergies. Treatments include medicines, allergy shots, and avoiding the substances that cause the reactions.

Start Here

Allergic Reactions (American Academy of Allergy, Asthma, and Immunology) Also in Spanish

Diagnosis and Tests

All About Allergy Testing (American Academy of Allergy, Asthma, and Immunology) Also in Spanish
Allergy Blood Test (National Library of Medicine) Also in Spanish
Allergy Skin Test (National Library of Medicine) Also in Spanish

Prevention and Risk Factors

Allergens and Irritants (National Institute of Environmental Health Sciences)
Allergy-Proof Your House (Mayo Foundation for Medical Education and Research) Also in Spanish

Treatments and Therapies

6 Things To Know About Complementary Health Approaches for Seasonal Allergy Relief (National Center for Complementary and Integrative Health)
Allergy Medications: Know Your Options (Mayo Foundation for Medical Education and Research) Also in Spanish
Allergy Shots: Could They Help Your Allergies? (American Academy of Family Physicians) Also in Spanish
Butterbur (National Center for Complementary and Integrative Health)
Decongestants: OTC Relief for Congestion (American Academy of Family Physicians) Also in Spanish
Nasal Wash Treatment (National Jewish Health) Also in Spanish

Related Issues

Allergic Bronchopulmonary Aspergillosis (ABPA) (American Academy of Allergy, Asthma, and Immunology) Also in Spanish
Allergies and Asthma: They Often Occur Together (Mayo Foundation for Medical Education and Research)
Colds, Allergies and Sinusitis - How to Tell the Difference (American Academy of Allergy, Asthma, and Immunology) - PDF Also in Spanish
Eosinophilic Esophagitis: MedlinePlus Health Topic (National Library of Medicine) Also in Spanish
Feel Better. Live Better. See an Allergist / Immunologist (American Academy of Allergy, Asthma, and Immunology) Also in Spanish
Is It Flu, COVID-19, Allergies, or a Cold? (National Institutes of Health) Also in Spanish
Marvels of Mucus and Phlegm: The Slime That Keeps You Healthy (National Institutes of Health) Also in Spanish

Specifics

Allergic Skin Conditions (American Academy of Allergy, Asthma, and Immunology)
Cockroach Allergy (Asthma and Allergy Foundation of America)
Dust Mite Allergy (Mayo Foundation for Medical Education and Research) Also in Spanish
Mold Allergy (Asthma and Allergy Foundation of America)
Nickel Allergy (Mayo Foundation for Medical Education and Research) Also in Spanish
Oral Hypersensitivity Reactions (American Association of Oral and Maxillofacial Surgeons)
Pet Allergy (Mayo Foundation for Medical Education and Research) Also in Spanish
Physical Allergy (Merck & Co., Inc.) Also in Spanish
Stinging Insect Allergy (American Academy of Allergy, Asthma, and Immunology) Also in Spanish
Sun Allergy (Mayo Foundation for Medical Education and Research) Also in Spanish

Genetics

Allergic asthma: MedlinePlus Genetics (National Library of Medicine)
Vibratory urticaria: MedlinePlus Genetics (National Library of Medicine)

Videos and Tutorials

Allergies (Medical Encyclopedia) Also in Spanish
Histamine: The Stuff Allergies are Made of (National Library of Medicine) Also in Spanish

Test Your Knowledge

Pet Allergy Quiz (American Academy of Allergy, Asthma, and Immunology)
Seasonal Allergy Quiz (Medical Encyclopedia) Also in Spanish

Statistics and Research

FastStats: Allergies and Hay Fever (National Center for Health Statistics)
Prevalence of Allergies the Same, Regardless of Where You Live (National Institute of Environmental Health Sciences)
Seasonal Allergies at a Glance: What the Science Says (National Center for Complementary and Integrative Health)

Clinical Trials

ClinicalTrials.gov: Hypersensitivity (National Institutes of Health)
ClinicalTrials.gov: Rhinitis, Allergic, Perennial (National Institutes of Health)

Journal Articles References and abstracts from MEDLINE/PubMed (National Library of Medicine)

Reference Desk

Overview of the Immune System (National Institute of Allergy and Infectious Diseases)

Find an Expert

American Academy of Allergy, Asthma, and Immunology
Find an Allergist/Immunologist (American Academy of Allergy, Asthma, and Immunology)
National Institute of Allergy and Infectious Diseases
National Institute of Environmental Health Sciences Also in Spanish

Children

All about Allergies (For Parents) (Nemours Foundation)
Allergy Relief for Your Child (Food and Drug Administration) Also in Spanish
Do Allergies Cause Asthma? (Nemours Foundation) Also in Spanish
Prevention of Allergies and Asthma in Children (American Academy of Allergy, Asthma, and Immunology) Also in Spanish
What Are Allergies (Nemours Foundation) Also in Spanish
What Is a Pediatric Allergist / Immunologist? (American Academy of Pediatrics) Also in Spanish

Teenagers

Allergies (Nemours Foundation)
Do Allergies Cause Asthma? (Nemours Foundation) Also in Spanish

Patient Handouts

Allergic reactions (Medical Encyclopedia) Also in Spanish
Allergic rhinitis - self-care (Medical Encyclopedia) Also in Spanish
Allergies (Medical Encyclopedia) Also in Spanish
Allergies, asthma, and dust (Medical Encyclopedia) Also in Spanish
Allergies, asthma, and molds (Medical Encyclopedia) Also in Spanish
Allergy testing - skin (Medical Encyclopedia) Also in Spanish
Angioedema (Medical Encyclopedia) Also in Spanish
Antihistamines for allergies (Medical Encyclopedia) Also in Spanish