Eating shrimp at dinner, getting stung by a bee during a hike or using new medicine from the pharmacy can cause allergic reactions. Some allergic reactions are mild and cause discomfort but occasionally can become serious and life-threatening very quickly. Knowing the difference can help you act fast and save a life.
Many people think that a serious allergic reaction always shows obvious signs right away. But often, symptoms start small and then suddenly get worse. What begins with itching or a few hives can quickly affect your breathing, blood pressure and heart.
“Allergic reactions can be different each time, even for the same person,” said Jelena Eremija, MD, an allergist and immunologist at Banner - University Medicine. "How bad they are depends on many things, like your current state of health, environmental or situational circumstances and what caused the allergy or route of exposure."
Here’s what you need to know about allergic reactions, when they become emergencies and what to do if they happen.
What is an allergic reaction?
An allergic reaction happens when your immune system overreacts to something that is normally harmless. This trigger is called an allergen.
Common allergens include foods such as dairy and wheat, insect stings, medications, latex, pet dander and pollen. When exposed, your body releases chemicals like histamine to fight the allergen. This can cause symptoms ranging from mild irritation to serious, life-threatening problems.
Mild allergy symptoms vs. emergency symptoms
Not every allergic reaction is an emergency. Mild reactions are common and often improve with antihistamines or by avoiding the trigger.
Signs of a mild allergic reaction
Symptoms may include:
- Sneezing
- Runny nose
- Mild itching
- Watery eyes
- Isolated rash or several hives
- Mild stomach discomfort
Dr. Eremija explained that other mild allergic reactions might also cause flushing or swelling of the lips or tongue, sometimes happening together. Usually, these mild reactions only affect parts of the body that come into direct contact with the allergen.
But severe allergic reactions are different. They can affect more than one part of the body at once and quickly become life-threatening.
What is anaphylaxis?
Severe allergy symptoms are serious and can quickly become life-threatening, leading to a condition called anaphylaxis that needs immediate medical help.
During anaphylaxis, your body reacts strongly and can cause:
- Your airways to narrow
- Swelling in the throat
- A sudden drop in blood pressure, which can even lead to shock (dangerous/severe drop in blood pressure)
- Difficulty breathing
“It usually happens quickly and can be deadly," Dr. Eremija said. “Severe anaphylaxis can affect your breathing and circulation and may occur without skin symptoms being obvious."
Warning signs that an allergic reaction is an emergency
Anaphylaxis usually begins within minutes of exposure. The symptoms can start out mild and then get worse quickly.
If you or someone else shows these signs, call 911 and use an epinephrine shot (like an EpiPen) right away:
- Trouble breathing: You might hear wheezing, feel short of breath, experience tightness in the chest, have rapid breathing or cough a lot.
- Swelling in the lips, tongue, or throat: Swelling inside the mouth or throat can block the airways quickly. You might feel tightness, have trouble swallowing, feel a lump in your throat or have a hoarse voice.
- Dizziness or fainting: Severe allergies can cause a serious drop in blood pressure. Signs include weakness, confusion, pale skin, passing out or a fast heartbeat.
- Severe stomach problems: Some people may have stomach cramps, nausea, vomiting or diarrhea.
Dr. Eremija said that some people might suddenly feel scared or a sense of doom. This can also be a sign of a serious allergic reaction. Children can appear fussy or distressed and uncomfortable.
Can anaphylaxis happen without hives?
Hives and swelling often happen with allergic reactions but not always. This means you can have a serious allergic reaction even if you don’t see a visible rash.
Instead, early signs may involve:
- Breathing changes
- Coughing
- Dizziness
- Vomiting
- Throat tightness
“You might feel fine at first and then suddenly have trouble breathing a few minutes later,” Dr. Eremija said. "Symptoms can also come and go. That’s why every severe allergic reaction should be taken seriously, even if it seems mild at first."
Common causes of severe allergic reactions
Food allergies
Food allergies are among the leading causes of anaphylaxis. Even a tiny amount of food can trigger a severe reaction in some people.
Common food triggers include:
- Peanuts
- Tree nuts
- Shellfish
- Fish
- Milk
- Eggs
- Soy
- Wheat
Insect stings
Bee, wasp and fire ant stings can trigger dangerous reactions. Symptoms may begin within minutes.
Medication allergies
Sometimes medications can cause severe allergic reactions, including:
- Antibiotics
- Pain medications (NSAIDs)
- Chemotherapy drugs
- Contrast dye used in imaging tests
- Any other medication
Latex
Latex is found in some gloves, balloons and medical products. Reactions can range from mild skin irritation to a severe allergic reaction.
Who is at higher risk for severe allergic reactions?
Anyone can develop anaphylaxis but some people are at higher risk. The risk factors include:
- Having a history of anaphylaxis
- Asthma, especially if not well controlled
- Food allergies
- Multiple allergies
- Mast cell disorders (a condition that causes the body's immune cells to overreact and trigger allergy-like symptoms)
- Exercise or increase in core body temperature
If you've had a severe allergic reaction before, you may be more likely to have another severe reaction in the future. Talk to your health care provider or allergist for steps you can take to prevent another reaction.
How to treat a severe allergic reaction
Step 1: Use epinephrine
Epinephrine is the first-line treatment for anaphylaxis. It works quickly to open the airways, increase blood pressure, reduce swelling and make it easier to breathe. If you think someone might be having anaphylaxis, don't wait to get help.
“Use epinephrine even if you're not sure," Dr. Eremija said. "The risk of not treating a serious allergy is worse than getting epinephrine when it's not needed. We say, ‘epi first, epi fast.'"
An EpiPen can save a life. Here’s when and how to use one.
Step 2: Call 911
Even if your symptoms improve, emergency care is still important. After being treated with epinephrine for a severe allergic reaction, you should be taken by ambulance to an emergency room. There, you can be monitored because your symptoms might come back hours later, a process called biphasic anaphylaxis. You might also have symptoms that last a long time and need more treatment.
Find a Banner Health emergency department closest to you.
Step 3: If you don’t have epinephrine
Call 911 if you think someone is having a severe allergic reaction called anaphylaxis and you don't have an EpiPen. While waiting for help:
- Have the person lie flat with their legs raised, if possible
- Loosen tight clothing
- Help them stay calm and still
- If they are vomiting or having trouble breathing, turn them onto their side
- Do not give food or drinks
- If they stop breathing or lose consciousness, start CPR if you are trained to do so
Can Benadryl stop anaphylaxis?
Many people first reach for Benadryl during an allergic reaction. While antihistamines can help with itching or hives, they do not prevent severe reactions like anaphylaxis.
“There is no substitute for epinephrine,” Dr. Eremija. "Antihistamines and steroids don't work as quickly as epinephrine and they can't treat the serious symptoms of anaphylaxis effectively."
Can allergies change over time?
A surprising fact about allergies is that they can develop later in life. You might have eaten shrimp for years without any problem and then suddenly become allergic. The same can happen with medications, insect stings and other triggers.
Even mild reactions in the past don’t mean future reactions will stay mild. That’s why it’s important to take allergic reactions seriously and talk with your health care provider about testing or follow-up care.
Some childhood allergies, like milk or egg allergies, may get better over time. But allergies to peanuts are more likely to last into adulthood.
Can I prevent anaphylaxis?
You may not be able to prevent severe allergic reactions but you can reduce your risk of a dangerous one:
- Avoid known triggers
- Carry an EpiPen
- Wear a medical alert bracelet
- Have an allergy action plan
Learn more tips about preventing anaphylaxis.
Takeaway
Mild allergy symptoms like sneezing, itching or an isolated rash are common. However, trouble breathing, a sore throat, swelling of the lips or tongue, dizziness or symptoms affecting more than one part of the body could be signs of a serious allergic reaction called anaphylaxis. If epinephrine is available, use it immediately and call 911.
If you have a severe allergic reaction, anaphylaxis, repeated reactions or if you are unsure what caused the reaction, see an allergy doctor. An allergist can help find what triggered your allergy and make a plan to keep you safe. Find a Banner Health allergist near you.
Frequently asked questions about allergic reaction emergencies
When should I call 911 for an allergic reaction?
Call 911 if an allergic reaction causes trouble breathing, throat tightness, swelling of the lips or tongue, dizziness, fainting, confusion, a weak pulse or symptoms in more than one body system.
What are the first signs of anaphylaxis?
Early signs may include itching, hives, swelling, throat tightness, coughing, wheezing, stomach cramps, vomiting, dizziness or feeling like something is very wrong.
Can an allergic reaction be serious without hives?
Yes. Anaphylaxis can happen without hives. Breathing trouble, throat tightness, dizziness, fainting or low blood pressure can be signs of a severe reaction even without a rash.
Can a mild allergic reaction turn severe?
Yes. Some reactions start mild and then worsen. Watch for breathing changes, throat symptoms, swelling, vomiting, dizziness or symptoms spreading to more than one body system.
Should I take antihistamines for anaphylaxis?
Antihistamines may help with itching or hives but they do not treat breathing problems, throat swelling or low blood pressure. Epinephrine is the first-line emergency treatment for anaphylaxis or severe allergic reactions.
What should I do if my child says their throat feels funny after eating?
Take it seriously, especially if there is coughing, swelling, hives, vomiting, wheezing or behavior changes. Follow your child’s allergy action plan and call 911 if anaphylaxis is suspected.
How fast does anaphylaxis happen?
Anaphylaxis can happen within minutes after exposure but sometimes it can develop later. Symptoms can worsen quickly.
Should I go to the emergency room after using an EpiPen?
Follow your allergy action plan and provider’s advice. Call 911 if the symptoms are serious, do not get better, come back or if you don’t have another dose of epinephrine.
Can adults suddenly develop allergies?
Yes. People can develop allergies at any age, even if they have never had problems before.
