A woman having an allergic reaction to flowers


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

Tablet and capsule pills
Zyrtec-D (Cetirizine and Pseudoephedrine) Oral: Uses, Side Effects, Dosage
Oral pill and capsule
Rayos (Prednisone) Oral: Uses, Side Effects, Dosages
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.
How Can You Stop a Runny Nose?
Baby with rash on face
What Causes Allergic Reactions on Your Face?
EpiPen (Epinephrine) – Injection: Uses, Side Effects, Dosages, Interactions
Tablet and capsule pill
Clarinex (desloratadine) - Oral: Use, Side Effects, Dosage, Interactions
A tree in 4 different states for each of the seasons (Tips for Managing Year-Round Allergies)
How to Manage Year-Round Allergies
Sad woman with allergies
The Link Between Allergies and Depression
Person sneezing after eating
Is There a Reason That You Sneeze After You Eat?
A Black man blows his nose.
Natural Ways to Relieve Allergies
Illustration of subcutanneous injection
Xolair (Omalizumab) Subcutaneous: Uses, Side Effects, Dosage
A father on paternity leave looking after small son indoors, blowing his nose. - stock photo
5 Ways to Soothe Your Child’s Allergy Symptoms
blood on tissue from nosebleed
Can Allergies Cause Nosebleeds?
Portrait of a young white and blonde woman turning on a new air purifier at her house
Do Air Purifiers Actually Work?
Person with long black hair stands on a busy sidewalk, blowing their nose
What Are the Best and Worst States for Allergies?
A woman suffering from hay fever while sunbathing in her garden.
What Time of the Year Can You Have Seasonal Allergies?
alpha-gal allergy
What Is an Alpha-Gal Allergy?
Person with long black hair stands on a busy sidewalk, blowing their nose
Fall Allergies: Symptoms, Causes, and Treatment
Woman sneezing
Don't suffer through allergy season without trying these steps.
Skin prick allergy test
Blood Tests vs. Skin Tests for Allergies
A person with brown skin sits in front of a tissue box, blowing their nose
Winter Allergies: Symptoms, Causes, and Treatment
Shot of a young woman working on her laptop while holding her baby
An Overview of Seasonal Allergies in Toddlers
Allergen Types and Triggers - Illustration by Sydney Saporito
What Are Types of Allergies?
Blurred person holds tissue to their nose in response to ragweed
Allergens: Types, Function, Risks
Person with long brown hair squints their eyes and holds their throat with their hand
Sore Throat and Allergies
Person with white skin and brown hair sits on a couch blowing their nose
How Do Allergies Work?
Illustration of nasal spray
Dymista (Azelastine and Fluticasone) Nasal: Uses, Side Effects, Dosages
Tips for Reducing Dust Mite Exposure - Illustration by Theresa Chiechi
What Is a Dust Mite Allergy?
Woman with headache rubbing forehead
What to Do About an Allergy Headache
Person with brown skin and long, brown hair blows their nose
What Are Respiratory Allergies?
A person wearing a white shirt blowing their nose into a tissue.
How to Get Relief From Allergy Symptoms
adult onset allergies - man covering nose with tissue
Adult-Onset Allergies
Woman touching ear
Can Allergies Cause Tinnitus?
Vacuuming carpet
Are You Allergic to Your Carpet?
Woman coughing
How to Treat and Allergy Cough
Woman Blowing Nose on Tissue Paper
What Are Severe Allergies?
What to Know About Latex Allergies
What to Know About Latex Allergies
Shot of a mature businesswoman wearing a mask and rubbing her throat in an office
Can Allergies Cause a Dry Throat?
Airborne allergies
Everything You Need to Know About Indoor Allergies
Treatment of Itchy Throat Allergies: Antihistamines, Lozenges or cough drops with a bag (lozenges and cough drops), hard candy, honey, humidifier and air purifier, water and other fluids, circles (saltwater gargle)
Itchy Throat & Allergies
Allergy Types - Illustration by Jiaqi Zhou
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?
Springtime Pollen in the air
Allergies or COVID-19: What Are the Differences?
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
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.