Allergic Reaction

What is an allergic reaction?

Allergic reactions are a set of symptoms that happen after you touch, inhale or eat something you’re allergic to. They can also happen after a bee sting. Examples of allergens that can set off allergic reactions include pollens, pets, dust, foods and medications.

Allergic reactions can be mild — maybe you get a small, itchy patch of skin where a dog licked you, or you get the sniffles after a few minutes outdoors on a spring day. But they can also be life-threatening, making it hard to breathe or dangerously dropping your blood pressure. Call 911 (or your local emergency service number) or get to an emergency room immediately if you have face, mouth or throat swelling, difficulty breathing or swallowing, or if you feel faint.

Examples

Specific types of allergic reactions include:

• Allergic rhinitis, symptoms like sneezing, coughing and wheezing due to airborne allergens
• Allergic asthma, when breathing in an allergen causes an asthma attack
• Contact dermatitis, when touching something causes an itchy rash, hives or blisters
• Oral allergy syndrome, itching or minor swelling of your lips, mouth, tongue or throat after eating fruits, vegetables or nuts
• Anaphylaxis, airway swelling, hives, vomiting and low blood pressure, which can be severe and potentially life-threatening

What are the symptoms of allergic reactions?

Symptoms of allergic reactions can include:

• An itchy rash or hives. This may look red or lighter or darker than the skin around it. It might be raised or bumpy. Skin reactions can happen when you touch or swallow something you’re allergic to, or after insect bites or stings.
• Runny nose, sneezing, itchy eyes, wheezing or coughing. These symptoms usually happen when you inhale an allergen.
• Vomiting, diarrhea or stomach pain (with or without other symptoms).
• Itching, tingling or swelling of your lips, mouth, tongue or throat.

Anaphylaxis is a type of severe, rapid allergic reaction that’s a combination of these symptoms and low blood pressure. It can be life-threatening if not treated right away.

What causes allergic reactions?

Allergic reactions happen when your immune system overreacts to something it mistakenly thinks is harmful. Common causes of allergic reactions include:

• Bee stings
• Cats, dogs and other animals
• Dust mites
• Foods like peanuts, tree nuts, eggs, shellfish and more
• Medications
• Molds
• Nickel and other metals
• Poison ivy, oak and sumac
• Pollen

Sometimes, the cause of a reaction is obvious. Other times, you might need to see an allergist or dermatologist to diagnose the cause. They can perform allergy skin or blood tests to determine what you could react to.

How do you stop an allergic reaction?

If you’re having a severe allergic reaction — you’re having difficulty breathing, you’re feeling dizzy, or your face, lips, tongue or throat are swelling — call 911 or get to the nearest emergency room. Use your epinephrine auto-injector (EpiPen® or Auvi-Q®) if you have one that’s prescribed to you.

For milder allergic reactions, you might get some relief with:

• Antihistamines like fexofenadine (Allegra®), loratadine (Claritin®), cetirizine(Zyrtec®) — these work best when taken before you’re exposed to an allergen, but can also help relieve symptoms of allergic rhinitis
• Steroid nasal spray (Flonase® or Nasacort®)
• Oral decongestants or saline rinses for nasal symptoms
• A cold washcloth or eye drops made for allergies to help relieve itchy eyes
• Showering and putting on fresh clothes to help remove lingering allergens on your body
• Hypoallergenic or fragrance-free lotions to help calm itchy rashes

In some cases, a healthcare provider might need to prescribe steroids to reduce inflammation.

How can I prevent allergic reactions?

If you have known allergens, avoiding exposure to them (eating, touching or inhaling them) is the best way to prevent an allergic reaction. Some strategies to reduce your risk of an allergic reaction include:

• Wear long sleeves, pants and gloves if you might come in contact with something like poison ivy. Afterwards, use soap that’s meant for removing grease and oil from your skin to wash your hands, arms and any other areas that could’ve been exposed.
• Regularly vacuum and use high-efficiency particulate (HEPA) air filters to help remove allergens from your home. Change the filters on your HVAC system regularly.
• Keep your windows closed during pollen season.
• If you have a food allergy, check food labels, keep allergen-free foods in your house, and only eat at restaurants where you know you can eat something that’s allergen-free.

Avoiding allergens isn’t always possible, and sometimes you’re accidentally exposed to something you’re allergic to. Your provider might recommend you take certain medications daily or get specific treatments regularly. Depending on the type of allergy, treatments that could reduce your risk of an allergic reaction include:

• Antihistamines
• Nasal sprays
• Leukotriene modifiers like montelukast
• Omalizumab (Xolair®) injections for food allergies
• Allergy immunotherapy, like allergy shots, sublingual immunotherapy (SLIT) or oral immunotherapy (OIT)

Always carry an epinephrine injector with you if you’re at risk for a severe allergic reaction.

When should you go to the ER for an allergic reaction?

Go to the ER or call 911 if you experience symptoms of a severe allergic reaction, including:

• Swelling of your face, lips, tongue or throat
• Difficulty breathing
• Chest pain or tightness
• Hives all over your body
• Tingling hands, feet or lips
• Feeling weak, dizzy or faint
• Feeling of dread or impending doom

What are the four types of allergic reactions?

Four types of allergic reactions (usually called hypersensitivity reactions) include:

• IgE-mediated reactions (type I). Also called “true allergies,” these cause most common allergies, like those to food, pollen and pet dander.
• Cytotoxic reactions (type II). These cause blood compatibility reactions (like Rh incompatibility) and some drug reactions.
• Immune complex reactions (type III). These can cause autoimmune disorders.
• Cell-mediated reactions (type IV). These cause delayed reactions like poison ivy rashes, latex allergies and Steven-Johnson syndrome.

When people talk about allergic reactions, they’re most often talking about either type I or type IV hypersensitivities.