An allergic reaction is the body's way of responding to an "invader." When the body senses a foreign substance, called an antigen, the immune system is triggered. The immune system normally protects the body from harmful agents such as bacteria and toxins. Its overreaction to a harmless substance (an allergen) is called a hypersensitivity reaction, or an allergic, reaction.
See the complete A-Z list of all the Allergies related information or browse the current list of select resources.
Allergies Related Resources
- How Are Food Allergies Done?
- What Are the Symptoms of Anaphylaxis?
- How Do You Know If You Have Hay Fever?
- What Is the Procedure for Testing for Allergies?
- Sinus Headache
- What Are the Signs of Anaphylaxis?
- What Causes Hives in Adults?
- Allergy: Poison Ivy, Oak, and Sumac
- Drug Allergy
- What Is Fluticasone Propionate Nasal Spray Used For?
- What Are Solone Tablets Used For?
- What Allergy Causes Bumps on Arms?
- Hives and Angioedema
- Allergic Reaction
- What Is Chlorpheniramine Maleate Used For?
Allergies Images and Slideshows
- Best and Worst Foods for Lung Health
- Allergies: Signs of a Severe Allergic Reaction
- Nasal Irrigation: Natural Relief for Cold & Allergy Symptoms
- Home Health: Meet the Bugs That Live In Your House
- Top Items for Your Allergy Relief Kit
- 12 Natural Ways to Defeat Allergies
- Reasons Why Your Face Looks Swollen
- Home Allergy Quiz: Is Your Home Allergy-Proof?
- Sinus Infection (Sinusitis) Symptoms & Treatment
- The Most Common Food Allergies for Kids and Adults
- Dangerous Allergies: Anaphylaxis and Life-Threatening Allergy Triggers
- Nasal Allergy Attack: Causes, Triggers, Treatments
- Bad Bugs: Identify Insects and Bug Bites
- Sinus Infection: Sinusitis Dos and Don'ts
- Allergies: Common Plants and Trees That Trigger Allergies