Allergic reactions to caffeine are very rare. Some believe that the symptoms associated with those who claim to be allergic to caffeine are not really allergic reactions, but are rather a product of caffeine sensitivity.
This seems like a logical approach given the way caffeine interacts with the body. Caffeine drives the adrenal glands to make stress hormones like adrenaline and cortisol. Ideally, this would make a person feel comfortably alert and awake. However, some people are sensitive to the induced adrenaline rush and experience muscle tension, rapid heart beat, fast pulse, and quick breathing. The affected persons can feel nervous and anxious, and thus irritable and restless. They can even experience insomnia. These negative reactions due to hyper-sensitivity can be confused with an allergic reaction to the caffeine itself. This doesn’t mean that there isn’t such a thing as an allergic reaction to caffeine, it just means that negative symptoms associated with caffeine consumption are not necessarily an allergic reaction.
This approach however does not readily explain the more bizarre symptoms experienced by some affected persons. The more bizarre symptoms include extreme itchiness, delusions, hallucinations, and the like – and may be in fact symptoms of a caffeine allergic reaction.
One study based on anecdotal evidence, suggests genetic evidence regarding the inability to process caffeine. Some may lack the genes responsible for the ability to process the caffeine molecule or those genes might be defective for some reason, thus causing a caffeine build-up in the person’s body.
Another study published in 2003 by researchers in Spain, details the case of a 21-year-old male who experienced anaphylaxis, a life-threatening type of allergic reaction, after ingesting coffee or multiple cola drinks. But foods containing minute traces of caffeine, like decaffeinated colas, tea and chocolate, did not cause allergic reactions (see our article on Decaf). Allergy skin testing and allergy blood testing for IgE allergic antibody were both positive for caffeine.
Allergy testing to caffeine would be required to definitely make a diagnosis of caffeine allergy.
An allergic reaction comes about when your immune system mistakes (in this case) caffeine as a noxious substance that threatens your body. To defend the body, IgE antibodies are released to attack the caffeine. This chemical action causes the production of some other chemicals that assist in defending the body from the harmful substance. One of these chemicals is histamine, which causes inflammation when released in soft tissue. Testing for caffeine allergy would involve performing various tests to determine whether your body is creating IgE antibodies when caffeine is introduced into your body.