An Overview of Caffeine Allergy

Symptoms, Causes, Diagnosis, and Treatment

Iced coffee with milk

Verywell / Zorica Lakonic 

Given the number of people who consume caffeine every day, it may be hard to imagine that caffeine allergy is a real thing. While most people consume the stimulant without issue, others may experience diarrhea, jitteriness, insomnia, and other symptoms.

This can be due to heavy consumption (more than 400 mg of caffeine per day, which is about four cups of coffee). But for some, it can occur after just one cup of java (95 mg caffeine). Negative reactions to modest amounts of caffeine may be due to a non-allergic food intolerance to it or, less commonly, an allergic response of the immune system—just like any other food allergy.

Caffeine Allergy vs. Intolerance

You may be acutely aware of how caffeine is affecting you, but it may be hard—both for you and your doctor—to immediately know if what you're experiencing is due to a food allergy or intolerance (if not overconsumption). There are some important nuances worth knowing, however.

Caffeine Allergy
  • Immune system reaction with IgE antibody

  • Skin rash, itching, hives

  • In extreme cases, anaphylaxis can develop

Caffeine Intolerance
  • Overly sensitive to caffeine's effects of suppressing adenosine and stimulating adrenaline

  • Jitteriness, insomnia, stomach upset

  • Can be distressing but is rarely serious

Caffeine Allergy

Caffeine allergy develops when the immune system incorrectly identifies caffeine as a harmful substance and releases an antibody, known as immunoglobulin E (IgE), into the bloodstream.

When this happens, the body will respond with inflammation, dilating blood vessels and tissues and triggering the development of rash, itching (pruritus), hives (urticaria), or swelling (edema). Skin rashes are perhaps the main differentiating features between a caffeine intolerance and a caffeine allergy. In addition to dermatologic symptoms, other features include:

  • Anxiety
  • Chest pain
  • Cold sweats
  • Dizziness
  • Fatigue
  • Headaches
  • Heart palpitations
  • Joint pain
  • Muscles aches

Unlike with some allergies, respiratory symptoms are uncommon. Food intolerance and caffeine allergies can manifest with symptoms in anywhere from a few minutes to two hours. However, with a caffeine allergy, the severity of symptoms is typically linked to the speed by which they develop.

Those that develop quickly may, in rare cases, progress to a potentially life-threatening allergic reaction known as anaphylaxis. While potentially distressing, a food intolerance is rarely serious.

Caffeine Intolerance

In contrast, food intolerance—also known as non-IgE-mediated food hypersensitivity or non-allergic food sensitivity—refers to having difficulty in digesting certain foods rather than an allergy to them.

Food intolerance is often caused by the lack of a specific enzyme needed to metabolize a specific nutrient (like lactose). Without the means to digest a food, symptoms such as bloating, diarrhea, gas, spasms, and stomach aches can readily occur.

With regard to caffeine, the intolerance is often caused by the effect it has on the endocrine system. When consumed, caffeine suppresses a chemical messenger known as adenosine, which helps you sleep, while stimulating the production of adrenaline, which triggers the "fight-or-flight" response.

When secreted in excess, adrenaline can cause jitteriness, insomnia, lightheadedness, facial flushing, rapid heartbeat, rapid respiration, profuse sweating, and stomach upset. If you have an underlying food intolerance, the symptoms may be magnified and cause visible distress.

Risk Factors

As with any other allergies, the underlying causes of a caffeine allergy are largely unknown. Genetics are believed to play a part.


Caffeine allergies are difficult to diagnose by symptoms alone. Even if a rash or hives develop, allergy testing is often needed to determine if the causal agent (allergen) is caffeine or some other associated ingredient. With coffee, it's even possible that certain types of beans or roasting techniques may be more problematic than others.

It is also possible that certain fungi on processed coffee or tea leaves may trigger an allergic response unrelated to caffeine. Many of these fungi produce spores that the body recognizes as biological threats, particularly if you have an existing mold allergy.

Allergy skin testing and IgE antibody blood tests are the fastest and most effective means to diagnose a caffeine allergy. Less commonly, genetic testing may be used to identify mutations in the ADORA2A gene (the same gene loosely associated with Parkinson's disease).

Positive tests will indicate caffeine allergy, while negative results will point toward intolerance.


If the allergy or intolerance is chronic and relatively mild, it is reasonable to stop coffee and other caffeine-containing products—tea, colas, chocolate, sports drinks, certain headache medications (like Anacin), and over-the-counter stimulants (like NoDoz)—to see if the symptoms either clear or recur.

If in doubt, read the product label to see if it contains any caffeine, coffee, coffee extract, chocolate, cacao, cocoa, tea, or cola syrup. Even a product labeled "decaffeinated" may contain trace amounts that can stimulate the central nervous system in especially sensitive individuals.

If allergy symptoms develop, an over-the-counter oral antihistamine can often help. Chronic or recurrent allergies may benefit from allergy shots used to desensitize you to the allergen.


Quitting caffeine is sometimes easier said than done. As with many other forms of withdrawal, caffeine withdrawal can cause headaches, fatigue, and irritability. In severe cases, you may even experience nausea and flu-like symptoms.

Caffeine withdrawal symptoms occur within 12 to 24 hours after stopping caffeine and take from two to nine days to fully subside.

There are several things you can do to wean yourself off caffeine with the least amount of stress:

  • Drink a non-caffeinated hot beverage in the morning if coffee is part of your morning ritual. Avoid decaf, which can contain up to 18 milligrams of caffeine. Opt instead for an herbal tea, warm apple cider, or a cup of hot water with lemon. There is also a caffeine-free product called Teeccino made of roasted chicory that is designed to taste like coffee.
  • Drink plenty of water throughout the day to reduce your craving for cola or caffeinated energy drinks. If you're used to cola, switch to sparkling water, which can keep you well hydrated without excess sugar.
  • Take a long walk or exercise to counteract fatigue. Fresh air may give you a much-needed boost when your energy starts to lag. Even a 20-minute workout can get your heart pumping and stimulate the production of endorphins to help elevate your mood and alertness.
  • Allow yourself time to rest. If you are used to drinking a lot of caffeine, there may be a couple of days when your body will "crash" when deprived of the stimulant. You can prepare for this by setting aside time for extra sleep and relaxation.

A Word From Verywell

When used in moderation, the effects of caffeine—such as increased alertness—are often beneficial. But while caffeine allergy is rare, it can cause profound illness and discomfort in those affected. If the symptoms develop rapidly and manifest with widespread hives, fever, difficulty breathing, facial swelling, rapid heart rate, or vomiting, call 911 or have someone rush you to the nearest emergency room. If left untreated, anaphylaxis can progress rapidly and lead to shock, coma, cardiac or respiratory failure, and death.

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