Caffeine, a natural drug contained in coffee, stimulates the central nervous system. It is possible to be allergic to caffeine. Symptoms of a caffeine allergy include hives, swelling, itching, and more.

Caffeine is found in a range of plants including coffee beans, tea leaves, and cacao pods. It is consumed all over the world in coffee, tea, and chocolate. Approximately 90 percent of people in North America consume caffeine every day.

While caffeine is safe for most people, some people have a caffeine intolerance or allergy. This article explores the symptoms of caffeine allergy, what causes it, and how it may be treated.

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Caffeine is a stimulant that makes people feel more awake and focused. However, it may cause a number of symptoms, including an allergic reaction in some people.

Drinking coffee and other caffeinated drinks is a cultural norm in the United States and many other countries.

Caffeine is a natural stimulant that affects the brain and central nervous system, making people feel more alert and focused. Many drink coffee during their working day, as they believe it makes them more productive.

Most people can safely drink up to 400 milligrams (mg) of caffeine a day, the equivalent of around four cups. However, some people are sensitive to caffeine and experience the following when they consume it:

People who experience these symptoms may have a non-allergic food intolerance to caffeine.

Intolerance is different from having a caffeine allergy. Caffeine allergies are rare, and the symptoms of a caffeine allergy are more serious than those of an intolerance.

The symptoms of a caffeine allergy include:

  • hives, an itchy rash made up of many red bumps
  • swelling of the lips and tongue
  • itchy mouth, lips, and tongue

If a person has a caffeine allergy, these symptoms may occur within an hour of consuming caffeine.

Some people may experience a severe allergic reaction in response to caffeine called an anaphylactic shock, as this 2015 study reports. It is important to note that this is very rare.

The symptoms of an anaphylactic shock may include:

  • severe facial swelling, including eyes, lips, face, and tongue
  • trouble breathing due to facial swelling
  • trouble speaking
  • wheezing
  • coughing
  • nausea, abdominal pain, or vomiting
  • rapid heartbeat
  • dizziness
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While some people who experience symptoms when drinking caffeine are allergic to it, others will have a non-allergic intolerance.

Caffeine affects different people in different ways. The effects that caffeine has on the body of someone who is allergic to it are not the same as for someone who is caffeine intolerant.

When a person consumes caffeine, it is absorbed into their bloodstream from their gut. It can then affect how different organs work.

In the brain, caffeine blocks the effects of chemical messengers that normally make a person sleepy. It may also increase levels of adrenaline in the blood, which makes the brain and body more alert.

For people who have a non-allergic caffeine intolerance, the rush of adrenaline from caffeine may cause them to experience symptoms.

In contrast, a person with a caffeine allergy has symptoms that are caused by an allergic reaction.

What causes the symptoms of an allergic reaction to caffeine?

The body of a person who is allergic to caffeine treats it as if it were an invader. When they consume caffeine, their body produces an antibody called immunoglobin E.

The antibody prompts their cells to release histamine, to try to flush out molecules it has mistaken as harmful. These molecules are called allergens. This results in inflammation, which can lead to hives, itching, and swelling.

Why does an allergic reaction to caffeine happen?

As one 2014 study suggests, people’s different response to caffeine is thought to relate to genetics. However, exactly what makes some people’s bodies treat caffeine as an allergen is not fully understood.

One study suggested that it might be the dust that comes from the beans before they are roasted that acts as an allergen.

A further study in 2017 suggested that a type of mold on coffee beans may be the cause of allergies.

As with other allergies, a doctor may perform a skin test to diagnose a caffeine allergy.

The doctor will place a small amount of the allergen on a person’s arm and monitor the skin for a reaction. If a rash appears, this may signal an allergy.

If a person experiences an allergic reaction after consuming caffeine, then over-the-counter antihistamines may help reduce any itching, swelling, or hives.

In very rare cases, a caffeine allergy may cause anaphylactic shock. This can be treated with an injection of epinephrine. People with severe allergies often carry a special pen to administer this.

If a person is showing signs of an anaphylactic shock, contact emergency services immediately.

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Cutting out chocolate and coffee will help to prevent the symptoms of a caffeine allergy.

When a person has a caffeine allergy or intolerance, the best way to prevent it is for them to avoid consuming anything containing caffeine. This may involve cutting out:

  • coffee
  • tea
  • chocolate
  • energy drinks

If a person is unsure whether something contains caffeine, it is a good idea for them to read the label.

Many people rely on caffeine to stay focused and alert during their working day. Caffeine is a drug, so cutting it out may cause withdrawal symptoms. These may include:

After a week of being free from caffeine, withdrawal symptoms normally pass.

If a person is trying to cut out caffeine, they may need to find other ways to stay alert. The following may help:

  • taking regular screen breaks
  • getting out for a walk at lunchtime
  • drinking plenty of water
  • getting enough sleep
  • eating healthful food

The outlook for caffeine intolerance and caffeine allergy is positive.

So long as a person who is allergic or intolerant to caffeine avoids consuming it, they should not experience any further symptoms.