Many people drink a cup of coffee in the morning to help them wake up. Caffeine, a natural drug found in coffee, stimulates the central nervous system. But if a person has a caffeine allergy, caffeine can have some irritating effects on the body.

Caffeine is found in a variety of plants, such as coffee beans, tea leaves, and cocoa pods. It is consumed in coffee, tea and chocolate all over the world.

Caffeine and Its Effects

Drinking coffee and other caffeinated beverages 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 people drink coffee on their workday because they believe it will make them more productive.

Most people can drink up to 400 milligrams (mg) of caffeine per day, which is equivalent to about four cups. However, some people are sensitive to caffeine and experience:

  • Rapid heartbeat,
  • Worry,
  • Tension,
  • Headache,
  • Sleep problem,
  • People experiencing these symptoms may have a food intolerance that is not allergic to caffeine.

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

Symptoms of a caffeine allergy

Symptoms of a caffeine allergy include:

  • Hives, an itchy rash consisting 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 appear within an hour of consuming caffeine.

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

Symptoms of anaphylactic shock may include:

  • Severe facial swelling, including eyes, lips, face and tongue
  • Difficulty breathing due to facial swelling
  • Speech problem,
  • Wheezing,
  • Cough,
  • Nausea, abdominal pain or vomiting,
  • Rapid heartbeat,

Causes of caffeine allergy and intolerance

Caffeine affects different people in different ways. The effects on the body of someone who is allergic to caffeine are not the same as those of someone with a caffeine intolerance.

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

Caffeine in the brain blocks the effects of chemical messengers that normally make a person sleepy. It can also increase adrenaline levels in the blood, making the brain and body more alert.

For people with non-allergic caffeine intolerance, it can cause them to experience symptoms of adrenaline spikes from caffeine.

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

Why is there an allergic reaction to caffeine?

People’s different responses to caffeine are thought to be related to genetics, as a 2014 study suggested. However, what causes some people’s bodies to view caffeine as an allergen is not fully understood.

One study suggested that it might be the powder that acts as the allergen in the roasted beans.

Another study from 2017 suggested that a type of mold on coffee beans could cause allergies.

Diagnosing caffeine allergy

As with other allergies, a doctor may do 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 indicate an allergy.

Treatments for caffeine allergy

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

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

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


When a person has a caffeine allergy or intolerance, the best way to prevent it is to avoid consuming anything that contains caffeine. This may include cutting:

  • Coffee,
  • Tea,
  • Chocolate,
  • Energy drinks.

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

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

  • Shake,
  • Headache,
  • Irritability,

After a week without caffeine, withdrawal symptoms normally pass.

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

  • Taking regular screen breaks
  • Take a walk at noon,
  • Drinking lots of water,
  • Sleep enough
  • Eating healthy food.