A woman having an allergic reaction to flowers

Allergies

Allergies are an abnormal immune system response against normally harmless substances called allergens, which include things like pollens, dust mites, and molds. The allergic person’s body reacts to allergens by releasing chemicals, including histamine and leukotrienes, that affect the skin, respiratory system, digestive tract, and more. These chemicals ultimately produce symptoms such as sneezing, runny nose, congestion, rash, and swelling. 

In some cases, allergies can even lead to life-threatening symptoms, such as anaphylaxis. The most common types of allergies include hay fever, asthma, food allergies, and atopic dermatitis (eczema). 

Allergies are among the most common reasons people visit the doctor.

Frequently Asked Questions

  • Can allergies cause a fever?

    Allergies do not cause fever, though they do cause other symptoms commonly associated with cold and flu, such as runny nose, watery eyes, and sore throat. Though allergic rhinitis is commonly called hay fever, a fever is not one of the symptoms of the condition.

  • Can allergies cause a cough?

    Yes, a cough is commonly associated with asthma, a type of allergic disease. In cough-variant asthma, the primary symptom is a dry, hacking cough that may be worsened by allergic triggers. Cough may also be present with sinusitis, a chronic condition marked by congestion and swelling in the sinuses that often affects people with allergic rhinitis and/or asthma.

  • How can you get rid of allergies?

    Treatment depends on the severity and type of allergic disease you have, but prescription and/or over-the-counter medications may help relieve symptoms. Holistic treatments may also be helpful, but the primary pillar of allergy treatment is to learn and avoid your allergen triggers. That may mean seeing an allergist to undergo allergy testing and creating a personalized treatment plan.

  • When is allergy season?

    The spring and fall are both considered to be allergy season, but specific timing depends on the type of allergen. Tree pollen is most prevalent in early spring, from January to April, while grass pollen hits its peak between late spring and early summer. From late summer to early fall, weed pollen is the main culprit.

  • What causes allergies?

    Allergies are caused by an immune system overreaction to a non-threatening trigger. Several different immune mechanisms may be at play, but immunoglobulin E (IgE) hypersensitivity reactions are the main factor behind allergies to insect stings, certain drugs, and foods. Allergies also tend to run in families (atopy), and environmental factors, such as secondhand smoke, can put you at greater risk.

Key Terms

woman sneezing in the garden
How Do You Know If You Have Allergies?
a sick woman blowing her nose
Allergies or Sinus Infection?
Sneezing and checking body temperature
Can Allergies Cause a Fever?
a sick woman coughing at home
Allergy Cough vs. COVID Cough: What Are the Differences?
young Asian woman pouring a cup of tea from a stylish transparent tea pot into a cup
Can Tea Help With Allergies?
Woman holding her throat
Is My Sore Throat Allergies or COVID?
Person with curly, brown hair and brown skin blowing their nose in bed
Morning Allergies: Causes, Symptoms, Prevention, and Treatment
A woman blowing her nose
What’s the Difference Between the Flu and Allergies?
photo of father and son with tissue.
Are Allergies Hereditary?
adult woman in the nature suffering allergy
An Overview of Environmental Allergies
Portrait of young black woman sneezing in to tissue at home. Sick african woman wrapped in blanket sitting on sofa blowing her nose at home. Ill girl sneezing with runny nose in winter.
Body Aches From Allergies
A young well-dressed woman blowing her nose on a rainy day in the city
Weather-Related Allergies
Girl wiping nose with tissue in a field
What to Know About Treating Allergies With CBD
A close up of a branch of a willow tree releasing pollen.
Trees that rely on the wind for pollination may be making you sneeze.
A young brunette girl holding a dandelion and rubbing her eyes.
Lots of kids experience eye allergies. Here's how to help them cope.
Woman with earache
What You Need to Know About Ear Pain and Allergies
Telehealth visit with doctor for allergies
Telehealth for Allergies
Woman itching her arm
How to Treat Mast Cell Activation Syndrome
Woman holding her head at her desk
Sick Building Syndrome Explained
Mold Growth on Wall and Damp Stained Wood Door
Flooding and Water Damage Can Trigger a Mold Allergy
Man blowing nose at home on the couch
Learn What the Different Seasonal Allergies Are and How to Treat Them
Family camping near a lake
How to Have an Allergy-Free Camping Trip
Blowing a dandelion
Pollen Counts Can Help People Know When They Could Have Allergies
tree allergy
What You Should Know About Seasonal Allergies and Pollen Allergies
A piece of moldy cheese
Mold, Food, and Penicillin Allergies
Woman blowing her nose
What Is Perennial Allergic Rhinitis?
Doctor giving man Immunotherapy
An Overview of Immunotherapy
Allergies and vitamin D deficiency
A Vitamin D Deficiency Can Make Your Allergies Worse
Stressed businessman
How Allergies Affect Your Mood and Energy Level
Great Lawn in Sunlight
Does the Green of Springtime Trigger Your Allergies?
Woman blowing her nose with a tissue
5 Reasons You Might Have an Itchy Face
Itchy eyes
How to Put a Stop to Itching
Woman scratching her skin
Can a Woman Be Allergic to Her Period?
Girl wiping nose with tissue
Is There a a Connection Between HIV and Allergies?
Close up of US nickel coins
Yes, You Can Have Allergic Reactions to Coins and Paper Money
151810914.jpg
Immunoglobulin A Deficiency
Woman eating a taco
Why Your Nose May Run When You Eat Certain Foods
Prenatal Yoga Breathing
Anaphylaxis During Pregnancy
overhead view of allergist holding ruler near marked hand of woman
What Is an Allergist?
Woman holding toothbrush
Could You Have a Toothpaste Allergy?
Person holding an open cream jar with some cream on fingers
Which Creams Are the Best for Treating Itchy Skin?
Latin woman with flu or allergies sneezes while outside. Winter.
What's Causing Your Winter Allergies?
Eye Drops for Allergies
The 8 Best Eye Drops for Allergies of 2021
Low Angle View Of Dandelion Blooming Against Sky
Why Would You Get an Allergy During the Summer?
A burger being flipped on a very smoky barbecue
Learn Why Your Barbecue Might Be the Culprit of Your Allergies
Close up of woman's nose and septum piercings
How to Deal With Body Piercing Allergies
Allergy Test, Child
Blood and Skin Testing For Allergic Reactions
A young girl with allergies in a field
Learn Everything You Should Know About Sensitization and True Allergy
Woman blowing nose, fall scene
What to Expect During Fall Allergy Season
Little boy sneezing
How Do You Know If Your Child Has Allergies?
Ragweed plants
All About Ragweed Allergy
Contact dermatitis rash on woman's neck - symptoms of contact dermatitis
Is That Itchy Rash Contact Dermatitis?
Allergy Test Kit
The 6 Best At-Home Allergy Tests of 2021
Mold found inside a bathroom wall during remodeling
How Mold Can Worsen Asthma
Woman sleeping in bed
Allergies and Asthma at Night Can Make Sleeping Difficult
Man using asthma inhaler
How Are Allergies Connected to Asthma?
Two kids playing near a pool
How Your Itchy Skin After Swimming May Be a Chlorine Rash
Man blowing nose
What Is Causing My Runny Nose?
Airborne allergies
What Are Airborne Allergies?
Man talking with doctor
Recovering From Nasal Polyps Surgery
Page Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Academy of Allergy Asthma & Immunology. Allergic reactions. Updated September 28, 2020.

  2. American Academy of Allergy, Asthma, and Immunology. Allergic reactions. Updated September 28, 2020.

  3. Murrison LB, Brandt EB, Myers JB, Hershey GK. Environmental exposures and mechanisms in allergy and asthma development. The Journal of Clinical Investigation. 2019 Apr 1;129(4):1504-15. doi:10.1172/JCI124612

  4. National Institute of Allergy and Infectious Diseases. Guidelines for the diagnosis and management of food allergy in the United States.