Signs and Symptoms of Caffeine Intolerance

Does it ever seem as if caffeine hits you a little bit harder than it does your friends? Maybe it's just that you get jittery or restless after only one cup of coffee, and these could be symptoms of a caffeine sensitivity or caffeine intolerance.

It's also possible to be allergic to caffeine, which could cause rashes or breathing problems. Only a doctor will be able to make an official diagnosis, but it is helpful to understand what effects coffee can have on someone who has a sensitivity or an allergy.

Remember that there's a big difference between a food intolerance and a food allergy. People who have life-threatening allergic reactions can get hives or a swollen tongue or throat, or they might start wheezing or coughing.

A person who is intolerant will have discomfort but nothing dangerous. Think of a person who has lactose intolerance: Milk products might make them gassy and bloated, or might even give them diarrhea, but they don't have their throat swell up.

​Read more:​ 5 Theories Why Gluten Intolerance Is Skyrocketing

This is similar to someone who has a caffeine intolerance. Someone who is intolerant of caffeine will feel the effects to a greater extent compared with someone who is not sensitive. The American Psychological Association notes that people who are caffeine sensitive experience side effects of overconsumption even if they have less than the recommended 400 milligrams a day, the amount in three of four cups of coffee.

Those people with a strong caffeine sensitivity will feel such side effects as restlessness, insomnia and a rapid heart beat, as listed by the American Psychological Association, as well as headaches, nervousness, jitters, an increase in blood pressure and a susceptibility to dehydration, all of which are listed by the Cleveland Clinic.

According to Harvard Health, this variation in sensitivity is influenced by genetics, and just as there are those who are especially sensitive to it, there are also those who are more tolerant and can have large amounts but feel barely anything.

While some people might claim they develop a coffee intolerance as they grow older — for example, they used to be able to drink a cup of coffee within a few hours of bedtime and still fall asleep, but now they no longer can — more people actually develop a tolerance to caffeine.

Cleveland Clinic describes a caffeine tolerance as the body's adjusting to the amount of caffeine it has every day. When that happens, you have to get more and more in order to feel the effects of it. So it's unlikely you will develop a coffee intolerance as you grow older.

The only way to get caffeine out of your system is to wait it out, and this can sometimes take up to 10 hours to happen. Drinking plenty of water helps because it will flush the caffeine out of you.

Caffeine allergies are uncommon, but some people do have them. Consider two rare but extreme cases of allergic reactions to caffeine observed by doctors, the first of which dealt with urticaria-angioedema, more commonly known as hives and swelling, and the second of which involved anaphylaxis, in which the blood pressure drops and airways narrow, thus preventing breathing.

The instance of hives was reported in a December 2014 article published in the ​Indian Dermatology Online Journal​, which detailed the experience of a young woman who required emergency care because of an outbreak of urticaria-angioedema. The 24-year-old was working in a supermarket and developed wheals on her lips, neck, groin, hands and feet. She also had itching eyelids, ears and tongue.

In other instances, the same woman had edema, diarrhea and loss of consciousness. Researchers observed that coffee consumption was linked to each of these reactions. The woman gave up caffeine, and after two years of avoiding it, she did not have any more instances of allergic reactions.

Based on this situation, the study determined that although situations are rare, it is possible that a caffeine allergy, or hypersensitivity to caffeine, could cause hives.

The instance of anaphylaxis due to caffeine consumption was recorded in a January 2015 study (albeit a small study focused on one person) published in ​Asia Pacific Allergy​. In this case, a 27-year-old woman had an allergic reaction after she ate a piece of candy with 42 milligrams of caffeine to prevent drowsiness.

After the allergic reactions manifested themselves, she recovered with medication, although the exact cause of her reaction was not clear. Five days later, she experienced other allergic reactions after drinking tea and eating coffee jelly, which indicated that these reactions were brought on by caffeine. After she gave up caffeine, she did not have any more allergic reactions.

The study noted that caffeine allergies are real, although they are less common than food-related allergies such as those to wheat or eggs. In other reported cases of allergic reactions due to caffeine, the caffeine had been combined with another drug. The only other case similar to this one, where reaction was caused by caffeine consumption alone, was that of a 9-year-old boy who had a reaction after he drank a cup of coffee.

If you think you might have a coffee intolerance or an allergy to caffeine, or hypersensitivity, you can start by avoiding coffee or other caffeinated beverages that might trigger a reaction. You should also talk to your doctor about being tested to know for sure.

According to the Baylor College of Medicine, there are two ways to test for food-related allergies. The first involves a skin test where liquid with the food protein is put on the skin, and the skin is pricked so that the liquid can then enter. If a hive develops, it can be concluded the patient is allergic to that food.

Another option is to run a blood test that will examine for food-specific antibodies. Neither this nor the skin test is perfectly accurate, and most food allergies must be diagnosed by a doctor who is able to closely observe the way a patient reacts to certain foods.

A caffeine intolerance doesn't mean you have to give up coffee entirely, though you might feel better if you reduce your intake. A caffeine allergy, on the other hand, could be life threatening and should be taken seriously.