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.

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Page Sources
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  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.