Allergies: Symptoms, Testing, Treatment, and When Reactions Are an Emergency
An allergy occurs when the immune system reacts to a substance that is usually harmless to most people. Allergic disease can affect the nose, eyes, lungs, skin or gastrointestinal tract and can range from mild symptoms to anaphylaxis.
Common types of allergy
- Allergic rhinitis from pollen, dust mites, mold or animal allergens
- Food allergy
- Drug allergy
- Insect-sting allergy
- Latex allergy
- Allergic skin disease such as hives or some forms of eczema
Possible symptoms
Sneezing, nasal congestion, itchy or watery eyes, hives, swelling, wheezing, vomiting or diarrhea can occur depending on the allergen and the organ system involved.
Trouble breathing, throat or tongue swelling, fainting, or a rapidly developing reaction involving multiple body systems can indicate anaphylaxis and requires emergency treatment.
Allergy versus intolerance or side effect
Not every reaction to food or medicine is an allergy. Food intolerance, medication side effects and other conditions can mimic allergic symptoms. Correct diagnosis matters because unnecessary avoidance can create nutritional or treatment problems.
How allergies are diagnosed
Diagnosis begins with the history: what exposure occurred, what symptoms followed, how quickly they appeared and whether the reaction has happened before. Skin-prick testing or specific IgE blood testing may be useful when guided by the clinical history.
Broad screening panels and IgG food testing are not recommended for diagnosing food allergy because they can produce misleading results.
Treatment
Treatment depends on the allergy and can include exposure reduction, antihistamines, nasal corticosteroids, other targeted medicines and allergen immunotherapy for selected inhalant or insect allergies. Food allergy management may include strict avoidance, emergency preparedness and selected specialist therapies.
Severe allergy
People at risk of anaphylaxis may be prescribed epinephrine and an emergency action plan. See Anaphylaxis: Symptoms, Epinephrine, and What to Do in an Emergency.
Editorial sources
This article provides general education and does not replace individualized allergy/immunology evaluation.
