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
- 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?
- Severe Allergic Reaction (Anaphylactic Shock)
- What Foods Are High in Allergens?
- How Long Is an Allergic Reaction?
- olopatadine (nasal) (Patanase) (Patanase)
- ciclesonide nasal (Omnaris, Zetonna) (Omnaris)
- levocetirizine (Xyzal) (Xyzal)
- acetaminophen, diphenhydramine, and phenylephrine (Benadryl Allergy and Cold) (Benadryl Allergy & Cold, Benadryl Allergy & Sinus Headache, Sudafed PE Severe Cold and more)
- desloratadine and pseudoephedrine (Clarinex-D 12 Hour, Clarinex-D 24 Hour) (Clarinex-D 12 Hour, Clarinex-D 24 Hour)
- chlorpheniramine and codeine (Codar AR, Tuxarin ER, Tuzistra XR) (Cotab A, Cotab AX, Notuss-AC and more)
- epinastine ophthalmic (Elestat) (Elestat)
- omalizumab (Xolair, Xolair Prefilled Syringe) (Xolair)
- diphenhydramine and phenylephrine (Benadryl Allergy Plus Congestion) (Alahist LQ, Aldex-CT, Children's Triacting Night Time and more)
- dexchlorpheniramine and pseudoephedrine (AllerDur, Deltuss DP, Rescon) (AllerDur, Duotan PD, Tanafed DP)
- desloratadine (Clarinex, Clarinex Reditabs) (Clarinex, Clarinex Reditabs)
- cetirizine and pseudoephedrine (All Day Allergy-D, Allergy D-12, Allergy Relief Nasal Decongestant) (All Day Allergy-D, Zyrtec-D)
- fluticasone nasal (Childrens Flonase, Flonase, Flonase Allergy Relief) (Flonase, Veramyst)
- flunisolide nasal (Nasalide) (Nasarel)
- beclomethasone nasal (Beconase AQ, Qnasl, Vancenase AQ) (Beconase AQ)
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