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Allergic Reaction

Overview

Allergies are an overreaction of the body's natural defense system that helps fight infections (immune system, Opens dialog). The immune system normally protects the body from viruses and bacteria by producing antibodies, Opens dialog to fight them. In an allergic reaction, Opens dialog, the immune system starts to fight substances that are usually harmless, such as dust mites, Opens dialog, pollen, or a medicine. It fights them as though these substances were trying to attack the body. This overreaction can cause a rash, itchy eyes, a runny nose, trouble breathing, nausea, and diarrhea.

An allergic reaction may not occur the first time you're exposed to an allergy-producing substance (allergen, Opens dialog). For example, the first time you are stung by a bee, you may have only pain and redness from the sting. If you're stung again, you may have hives, Opens dialog or trouble breathing. This is caused by the response of the immune system.

Many people will have some problem with allergies or allergic reactions at some point in their lives. Reactions can range from mild and annoying to sudden and life-threatening. Most allergic reactions are mild. Home treatment can relieve many of the symptoms. A reaction is more serious when a severe allergic reaction (anaphylaxis, Opens dialog) occurs, when allergies cause other problems (such as nosebleeds, ear problems, wheezing, or coughing), or when home treatment doesn't help.

Allergies often occur along with other problems, such as asthma, Opens dialog, ear infections, Opens dialog, sinusitis, Opens dialog, and sleep apnea, Opens dialog.

Types of allergies

There are many types of allergies. Some of the more common ones include:

  • Food allergies. They are more common in children than adults. Food allergies are most common in people who have an inherited tendency to develop allergic conditions. These people are more likely to have asthma and other allergies.
  • Medicine allergies, Opens dialog. Many prescription and nonprescription medicines can cause an allergic reaction. These reactions are common and unpredictable.
  • Allergies to insect venom, Opens dialog. When you are stung by an insect, poisons and other toxins in the insect's venom enter your skin. It's normal to have some swelling, redness, pain, and itching at the site of a sting. An allergic reaction to the sting occurs when your body's immune system overreacts to the venom of stinging insects.
  • Allergies to animals. These are more likely to cause breathing problems than skin problems. You may be allergic to your pet's dead skin (dander), urine, dried saliva, or hair.
  • Allergies to natural rubber (latex). Some people develop allergic reactions after repeated contact with latex, especially latex gloves.
  • Allergies that develop from exposure to a particular inhaled substance in the workplace. These allergies may be called occupational asthma.
  • Allergies to cosmetics, such as artificial nails, hair extensions, and henna tattoos.

Seasonal allergies show up at the same time of the year every year. They are caused by exposure to pollens from trees, grasses, or weeds.

Allergies that occur for more than 9 months out of the year are called perennial allergies.

Year-round symptoms (chronic allergies) can occur from exposure to animal dander, Opens dialog, house dust, or mold.

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Current as of: October 25, 2024

Author: Ignite Healthwise, LLC Staff

Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.