Have you ever had a painful stomach ache or felt lethargic after eating something sugary? Same. But could that mean you’re allergic to sugar, or is something else going on? In many cases, feeling crappy post-sweets is really just a “sugar hangover” that happens if you eat a ton of sugar. That sugar overload can cause your blood sugar to spike, then crash and burn. While it’s extremely rare to have a real sugar allergy, some people may be super sensitive to even a small amount of the sweet stuff.
“There are people who cannot tolerate high sugar intake,” Tanya Freirich, M.S., RDN, tells SELF. “Often, people will get a headache and other symptoms from the sugar ‘high’ and reactive ‘low.’” But that’s still not necessarily an allergy, which we’ll get to in a bit.
An important thing to remember when we talk about sugar intake is the difference between naturally occurring sugars and added sugars. Naturally occurring sugars would include those that are inherently part of the food and not added in during processing—like the sugar that’s naturally found in fruits, vegetables, and many dairy products. Added sugars, on the other hand, are any sugars that were put in during the manufacturing process—whether it’s honey, high-fructose corn syrup, or something else.
Listen, sugar is delicious. And having sugary foods, if they strike your fancy, can absolutely be part of a healthy, well-rounded diet. That’s true whether they’re naturally occurring or added. But if you have questions about a pattern you’ve noticed in how your body feels post-sugar, it can be helpful to know that while our bodies can’t really tell the difference between the sugar in a piece of fruit and the sugar in a candy bar, it’s true that many foods with a lot of added sugar also happen to not have a lot of certain other nutrients—like fiber—that can help your body slow the breakdown and absorption of sugar in the bloodstream, leading to a less drastic blood sugar spike. That could be why you feel more of a sugar high after eating a bunch of sweets than after eating a bunch of fruit. Ready to keep reading all about sugar? Let’s dive in.
Why some people feel strange after eating sugar
When sugar enters the body, it causes your blood glucose level to rise, which then prompts the pancreas to release insulin to help move that glucose from the bloodstream into the cells, according to the National Institute of Diabetes and Digestive and Kidney Diseases. A large release of insulin can also result in a sugar crash later on, which you may experience as a headache, nausea, or gastrointestinal upset, Lauren Harris-Pincus, M.S., RDN, author of The Everything Easy Pre-Diabetes Cookbook, tells SELF.
Some people may experience this more drastically than others, especially if they’re prone to high blood sugar, or hyperglycemia, which happens when there’s a buildup of excess glucose in the bloodstream. This is typically an issue for people with diabetes or prediabetes, but it’s possible to have these conditions and not even know it, so it’s worth knowing the symptoms to watch out for. Signs of high blood sugar include fatigue, increased thirst, frequent urination, headaches, and blurred vision, among others.
But it’s also possible that you’re having a reaction to the sugar itself, which can happen if you have an allergy or intolerance to certain ingredients.
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The difference between a sugar allergy and sugar intolerance
Everyone has certain foods that just don’t sit right with them, or that cause not-so-desirable symptoms like indigestion, painful bloating, or cramping. But that doesn’t necessarily mean you have a true allergy to that food or ingredient. And while some people use the terms interchangeably, a food allergy and a food intolerance are two different things.
A food allergy is a reaction that occurs when your immune system overreacts to a food protein, thinking that it’s a harmful substance. According to Food Allergy Research & Education (FARE), symptoms of a food allergy can range from mild to life-threatening and include:
- Hives
- Abdominal pain or cramping
- Diarrhea
- Sneezing
- Trouble breathing
- Anaphylaxis (a severe, life-threatening allergic reaction)
A food intolerance means that you have trouble digesting whatever that food is. In general, this causes digestive issues, and the symptoms are not as severe as those of a food allergy, per the Mayo Clinic.
There are a variety of reasons that you could be intolerant to a particular food. Sometimes it’s a result of your body not producing an enzyme necessary to break that food down (for example, if you’re lactose intolerant, you lack the enzyme lactase that’s needed to break down lactose, the sugar in milk). Other times it has to do with an underlying health condition, like irritable bowel syndrome (IBS), or even stress or anxiety, the Mayo Clinic says.
According to the American Academy of Allergy, Asthma, and Immunology, symptoms of a food intolerance include:
- intestinal gas;
- bloating;
- abdominal pain;
- diarrhea.
It’s easy to confuse an intolerance and an allergy because the symptoms can overlap (we’re looking at you, diarrhea and abdominal pain). But a major difference is that food intolerances are not the result of an immune system dysfunction. What’s more, people with food intolerances may be able to have a small amount of the food without any issues (or they can take something to help aid digestion), whereas with an allergy, you generally can’t have any of the food allergen.
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How to know if you’re allergic to sugar
While an intolerance to a certain type of sugar is fairly common, it’s extremely rare to have a true allergy to sugar. In fact, there seems to just be one documented case of fructose-induced anaphylaxis, which was published in a 2018 letter to the editor in the Journal of Allergy and Clinical Immunology: In Practice1.