Allergic reactions range from mild irritation to life-threatening anaphylaxis. Common forms include seasonal allergic rhinitis, food and drug allergies, insect-sting reactions, and allergic asthma. Diagnosis uses skin or blood testing; treatment includes avoidance, antihistamines, corticosteroids, inhalers for asthma, and immunotherapy for long-term control. Carry epinephrine and seek emergency care for breathing difficulty, throat tightness, facial swelling, fainting, or fast pulse.

How allergic reactions happen

Your immune system protects you from infections by recognizing and fighting harmful invaders. In an allergic reaction, the immune system mistakenly identifies a harmless substance (an allergen) as dangerous and mounts an unnecessary response. That response can range from mild irritation to a life-threatening emergency.

Common allergy types

Seasonal allergies (hay fever)

Also called allergic rhinitis, seasonal allergies are triggered by airborne pollens from grasses, trees, and weeds. Symptoms often include sneezing, runny or congested nose, itchy eyes, and postnasal drip.

Food allergies

Some people react to food proteins such as milk, eggs, peanuts, tree nuts, shellfish, soy, wheat, and others. Reactions can develop at any age. Symptoms range from hives and stomach upset to anaphylaxis, a severe whole-body reaction that requires immediate treatment.

Drug and medication allergies

Prescription or over-the-counter medicines can cause allergic reactions in some people. Reactions vary from mild rashes to severe systemic responses. Always tell your providers about previous drug allergies.

Insect stings

Most insect stings cause localized pain, redness, and swelling. A minority of people develop large local reactions or systemic allergic responses. People with a history of systemic reactions should carry emergency medication and get specialist advice.

Asthma triggered by allergies

Allergic asthma occurs when inhaled allergens - such as pet dander or dust mites - trigger airway inflammation, wheeze, shortness of breath, and coughing.

Recognizing severe reactions

Seek emergency care if you or someone else has difficulty breathing, tightness in the throat, swelling of the face or tongue, fainting, or rapid pulse. These signs may indicate anaphylaxis, which requires immediate intramuscular epinephrine and urgent medical attention.

Diagnosis and standard treatments

Allergy testing (skin-prick tests or blood tests for allergen-specific IgE) helps identify triggers. Management commonly includes:

  • Avoiding known allergens when possible.
  • Antihistamines for mild itching or sneezing.
  • Intranasal corticosteroids for allergic rhinitis.
  • Short courses of oral corticosteroids for severe inflammation when prescribed.
  • Inhaled controller medications and rescue inhalers for allergic asthma.
Allergen immunotherapy (allergy shots or sublingual tablets) reduces sensitivity for some inhalant allergies and can improve long-term control. For certain food allergies, specific oral immunotherapy programs are available under specialist supervision.

Practical tips

Read food labels and ask about ingredients when eating out. Control indoor triggers by washing bedding, reducing indoor humidity to limit dust mites, and keeping pets out of bedrooms if pet dander triggers symptoms. If you have had a severe allergic reaction, carry an epinephrine auto-injector and get an individualized emergency action plan from your clinician.

Allergic reactions are common but treatable. Work with a primary care provider or allergist to identify triggers and build a safe, effective plan.

FAQs about Allergic Reactions

What is anaphylaxis and how is it treated?
Anaphylaxis is a severe, rapid allergic reaction that can affect breathing and blood pressure. Treat it immediately with intramuscular epinephrine and get emergency medical care. People at risk should carry an epinephrine auto-injector and an action plan.
How are allergies diagnosed?
Clinicians use a medical history plus allergy tests such as skin-prick testing or blood tests for allergen-specific IgE to identify triggers. Testing should be interpreted with clinical context by a healthcare professional.
Can allergies be cured?
Allergies are often manageable rather than curable. Allergen immunotherapy (shots or sublingual tablets) can reduce sensitivity to certain inhaled allergens and improve symptoms long-term for many patients.
What should I do after an insect sting?
For most stings, clean the area, apply cold compresses, and take oral antihistamines or pain relievers as needed. Seek urgent care if you develop widespread hives, breathing difficulty, or throat tightness.
How can I reduce indoor allergy triggers?
Wash bedding regularly in hot water, reduce indoor humidity, use allergen-proof covers for mattresses and pillows, vacuum with a HEPA filter, and keep pets out of bedrooms if they trigger symptoms.