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Basics

• Summary
• Start Here
• Diagnosis and Tests
• Prevention and Risk Factors
• Treatments and Therapies

Learn More

• Related Issues
• Specifics
• Genetics

See, Play and Learn

• Videos and Tutorials
• Test Your Knowledge

Research

• Statistics and Research
• Clinical Trials
• Journal Articles

Resources

• Reference Desk
• Find an Expert

For You

• Children
• Teenagers
• Patient Handouts

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)

• Article: Allergen Immunotherapy: Pitfalls, Perks and Unexpected Allies.
• Article: Obesity: Next game changer of allergic airway diseases?
• Article: Complement's involvement in allergic Th2 immunity: a cross-barrier perspective.
• Allergy -- see more articles

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