Caffeine Allergy

Caffeine Allergy vs Caffeine Intolerance

In this article we will look at caffeine allergy and caffeine allergy symptoms and how they differ from caffeine intolerances.


Coffee has become a popular drink. Many of us have it first thing in the morning to wake us up; and then throughout the day while we’re socialising or need an energy boost. We use it to help move our bowels, to stimulate alertness, and even as a caffeine supplement for increasing metabolism and weight loss.


However, not all the effects of caffeine are positive. Some people react badly to caffeine or can’t tolerate drinking even small amounts of coffee. If you feel sensitive to drinking coffee, then this blog is for you. Today we’re looking at caffeine intolerance, how to tell if you have it, what causes an allergy to caffeine, how to differentiate between a caffeine intolerance and a caffeine allergy, and how to test for caffeine intolerance.

What is caffeine intolerance?

A caffeine intolerance is an undesirable reaction to consuming caffeine. If you have an intolerance to caffeine, you may be able to have only small amounts of caffeine, or not be able to have it at all because of the way that it makes you feel.


It is commonly believed that most people should be able to tolerate 400mg of caffeine in one day without experiencing negative effects. This is equivalent to about four cups of homemade coffee. However, some people can only tolerate as little as 19-40mg of caffeine a day before experiencing symptoms.

Caffeine Allergy

Symptoms of caffeine intolerance

If you have an intolerance to caffeine, you may experience:


  • a headache or migraine
  • poor sleep
  • restless legs
  • jittery, trembling, or shaky movements 
  • digestive upset
  • loose stools or diarrhoea
  • a hit of energy, followed by fatigue
  • irritability or restlessness
  • a racing heartbeat or palpitations
  • high blood pressure
  • anxiousness
  • fidgeting or jumpiness
  • light-headedness
  • facial flushing (red checks)
  • feeling sweaty or clammy


Caffeine may be a trigger for symptoms of irritable bowel syndrome (IBS) and depression (though caffeine is not believed to cause these conditions, only aggravate them).

Caffeine Sensitivity

Caffeine Sensitivity

Caffeine intolerance vs caffeine allergy

A caffeine intolerance is different to a caffeine allergy. 

An allergy to caffeine is caused by your immune system. It happens when your immune system mistakenly thinks that caffeine is dangerous, and it reacts to it in order to protect you. Unfortunately, this reaction can be severe, and can even be life-threatening (a reaction called anaphylaxis). 

If you have an allergy to caffeine, the symptoms happen faster than if you have a caffeine intolerance. Caffeine allergy symptoms can happen within seconds of having caffeine, while symptoms of intolerance can take between 15-60 minutes to occur.

The symptoms of caffeine allergy include:

  • itchy skin or hives
  • swelling of the lips, throat or tongue
  • dizziness
  • heart palpitations

If you have an allergy to caffeine you could have a severe anaphylactic reaction, the symptoms may include:

  • difficulty breathing (because of a swollen tongue or throat)
  • coughing
  • wheezing
  • fainting or loss of consciousness

Caffeine Allergy Rash

Caffeine intolerance is often less severe than a caffeine allergy, and it does not trigger your immune system. A food intolerance is generally caused by an issue with digesting and breaking down the food. In the case of caffeine, the intolerance is caused by not eliminating caffeine properly, and by the effect caffeine has on your hormones.

Caffeine intolerance is thought to be caused by:

  • a drop in adenosine. an issue with a liver enzyme
    Adenosine is a special chemical that reduces your blood pressure and helps you sleep. Caffeine blocks adenosine, and by doing so, it increases your blood pressure and prevents you from sleeping well.
  • being sensitive to too much adrenaline.
    Caffeine is a stimulant, and it gets your adrenal glands to produce adrenaline. Adrenaline can make you feel hyperactive and anxious. It triggers your “fight or flight” response and can lead to the symptoms of caffeine intolerance.
  • a gene mutation.
    Your liver uses a particular enzyme to break down and eliminate excess caffeine. However, if you have a mutation of the gene that produces this enzyme (the CYP1A2 gene), then caffeine will build up in your body.
  • medications.
    Some medications increase the intensity and side effects of caffeine. This includes medications like oral contraceptives (often referred to as ‘the pill’) and theophylline (used for lung conditions like asthma).

Coffee Makes Me Itchy

Coffee Allergy Symptoms

Sources of caffeine

Caffeine is a natural substance found in several plants and food products, including:

  • coffee beans
  • black tea
  • green tea
  • cacao beans (used to make chocolate)
  • kola nuts (used to make cola and cola drinks)

It can also be used to flavour foods such as ice-cream, puddings, protein powders, snack bars, breakfast cereals, and alcoholic drinks. It is in chocolate-flavoured foods, soft drinks (especially those with cola), and in some sports drinks. Small amounts of caffeine can sometimes even be found in decaf coffee and tea.

Caffeine Sensitivity Test

Low Caffeine Tolerance

Testing for caffeine intolerance

If you’re unsure whether or not you have an intolerance to caffeine, then the first place to start is to test for it. Our intolerance test is a quick and non-invasive way to test for caffeine intolerance, and you can do it in two easy steps. First, order your test HERE. Then send us a sample of your hair. That’s it! Once our lab receives your sample, we guarantee to get your results to you within three days. This ensures that you get your results fast, and you know for certain if you are intolerant to caffeine or other foods.

Takeaway points

Today we learnt all about caffeine intolerance. We looked at the main symptoms that you can expect if you have an allergy to caffeine, and how an intolerance differs to a caffeine allergy. We learnt that caffeine intolerance is caused by not properly eliminating caffeine, or by the effect caffeine has on your adenosine and adrenaline levels. By changing the level of these chemicals in your body, caffeine can make you feel jittery, unable to sleep, or have other symptoms of intolerance that we explored in-depth today. We discussed the plants and foods that caffeine can found in, and the test that you can do to determine if you have caffeine intolerance. The test takes two steps: to simply order the test HERE and send the lab your sample. This way you can know for sure whether you have caffeine intolerance!


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