While not all the effects are visible, anaphylaxis can cause noticeable symptoms such as swelling, hives, and skin flushing. It’s important to seek medical help as soon as symptoms begin.

Anaphylaxis is a potentially life threatening reaction to an allergen. You are at risk of experiencing anaphylaxis if:

  • you’ve ever had an anaphylactic reaction
  • you have allergies or asthma
  • a member of your family has experienced an anaphylactic reaction

Anaphylaxis happens quickly and causes serious symptoms throughout your body. Without treatment, anaphylaxis can lead to serious health effects and even death.

Becoming familiar with this information could help you recognize the symptoms in time to save a life.

Anaphylaxis happens when your immune system overreacts to an allergen (a substance that you’re allergic to). When an allergen enters your body, your immune system identifies that substance as a threat and tries to destroy it.

Anaphylaxis may happen seemingly out of nowhere or after you’ve avoided a known allergen for years. Some people experience exercise-induced anaphylaxis, in which a combination of exercise and allergen exposure leads to anaphylaxis.

Those who have experienced anaphylaxis often describe an early “weird” feeling or a “feeling of impending doom.”

Because the reaction involves your whole body, you may begin to feel like something is happening before any visible symptoms begin.

You might feel anxious, as if something is wrong, but may not be quite sure what it is. A rapid heart rate may accompany this feeling, contributing to the overall sense of anxiety.

One of the first visible symptoms of anaphylaxis is usually skin redness or other discoloration. This will often occur on your cheeks and may look like flushing, but it will not be accompanied by sweating. It can also develop on your chest, your neck, or other areas of your body.

You might then develop hives, which are itchy, raised welts on the surface of your skin.

The itching can be intense, but it’s important not to scratch, as doing so can lead to wounds and possible scarring.

The affected area may also feel warm to the touch.

The swelling or inflammation will likely spread. Inflammation is a key sign of immune activity and often signals an allergic reaction.

Your eyes, lips, tongue, hands, feet, and other areas of your face and body may swell up rapidly. Some people’s eyes may swell shut, or their lips may increase in size.

Parts of your body that have swelled up might also itch and tingle. For instance, itchy, swollen eyes are common in an anaphylactic reaction.

While your body is swelling, other symptoms may occur, including:

  • nasal congestion
  • sneezing
  • a runny nose

Your tongue may swell, and your throat and chest may tighten up, leading to symptoms such as:

  • coughing
  • trouble breathing
  • difficulty swallowing
  • wheezing

These are some of the more dangerous symptoms that can lead to a lack of oxygen and other serious health effects.

Anaphylaxis can quickly affect your digestive system, causing symptoms such as:

  • cramps
  • nausea
  • diarrhea
  • vomiting

You might also have general abdominal pain or even an urge to rush to the bathroom.

These symptoms are common with food allergies or medication allergies and may last hours after the initial reaction.

If you feel lightheaded, you could be experiencing a drop in blood pressure. This is related to changes in your heart and blood vessel function due to anaphylaxis.

The chemicals flooding your bloodstream may cause tiny blood vessels to widen, which will lower your blood pressure and potentially cause dizziness.

Your heart rate might also speed up as your heart tries to compensate for the drop in blood pressure.

People with existing heart disease have a greater risk of cardiac symptoms from anaphylaxis and may experience a heart “spasm.” This happens when one of the arteries in the heart narrows, reducing blood flow to the heart and resulting in chest pain.

In some cases, the heart might suddenly stop working — this is known as cardiac arrest.

Just as the release of histamine and other chemicals may affect your heart and chest, it can also cause changes in your brain.

You may experience headaches, confusion, and anxiety and have trouble speaking clearly.

Your vision may become blurry. In some cases, you might even faint or lose consciousness.

Seizures may occur in rare cases.

Becoming familiar with these symptoms can help you take immediate action when you notice them, either in yourself or in someone else. If you see someone experiencing an anaphylactic reaction, call an ambulance. If the person has an epinephrine auto-injector (often known by the brand name EpiPen), help them use it.

Anaphylaxis is a severe allergic reaction that causes symptoms throughout your body. Not all the effects are visible, but noticeable symptoms such as skin flushing, hives, and swelling can occur.

It’s important to seek help as soon as you notice anaphylaxis symptoms in yourself or someone else. Call 911 or go to the hospital right away. If you have an epinephrine auto-injector, use it as quickly as possible. Prompt treatment can be lifesaving.