Eno is an effervescent antacid powder that neutralizes stomach acid to provide fast relief from heartburn and acid indigestion. It works within seconds of dissolving in water, making it one of the quickest over-the-counter options for settling an upset stomach. The product is especially popular in South Asia, Latin America, and parts of Africa and Europe.
What Eno Is Made Of
A standard 5-gram dose of Eno contains three active ingredients: sodium bicarbonate (about 2.3 g), citric acid (about 2.2 g), and a small amount of sodium carbonate (0.5 g). In the sachet, these ingredients sit as a dry, inert powder. Nothing happens until you add water.
The moment the powder hits water, the sodium bicarbonate and citric acid react together, producing carbon dioxide gas. That’s what creates the familiar fizz. The resulting solution is mildly alkaline, which is exactly what your stomach needs when it’s producing too much acid. Eno comes in several flavors, including original, lemon, mint, and orange. The active ingredients are nearly identical across variants, with only minor differences in proportions.
How It Works in Your Stomach
Your stomach lining constantly produces hydrochloric acid to break down food. Sometimes it makes too much, especially after spicy meals, alcohol, or stress. That excess acid causes the burning feeling of heartburn or the discomfort of indigestion.
When you drink the dissolved Eno solution, the leftover sodium bicarbonate and sodium carbonate act as weak bases. They react with hydrochloric acid almost instantly, converting it into salt, water, and carbon dioxide. A clinical study measuring stomach pH found that Eno raised acidity levels within 6 seconds of reaching the stomach. That speed is the product’s main selling point: you feel the relief almost immediately.
The carbon dioxide produced during this reaction is what causes burping after you drink Eno. For many people, that belch itself brings a sense of relief, especially if bloating or gas was part of the problem.
What Symptoms It Relieves
Eno is designed for temporary relief of two specific problems: heartburn and acid indigestion. Heartburn is that burning sensation behind your breastbone, often worse after eating or lying down. Acid indigestion is the broader discomfort, heaviness, or nausea that comes from your stomach struggling with excess acid.
Eno does not treat the underlying cause of these symptoms. It simply neutralizes the acid that’s already there. If heartburn keeps coming back, that points to something worth investigating rather than masking with repeated doses of antacid.
Sodium Content and Who Should Be Careful
Each 5-gram dose of Eno contains roughly 0.85 grams of sodium. That’s a significant amount, comparable to about a third of the daily sodium limit recommended for people with high blood pressure. If you’re on a sodium-restricted diet for blood pressure, heart, or kidney reasons, taking multiple doses of Eno can push your sodium intake well above safe levels.
Eno is also not a good fit during pregnancy without medical guidance. Sodium bicarbonate can disrupt electrolyte balance, and the high sodium content adds an extra concern. Pregnant women dealing with heartburn (which is extremely common, especially in the third trimester) have safer, purpose-built alternatives available.
Side Effects of Regular Use
Occasional use of Eno is generally well tolerated. The most common side effects are mild: bloating, burping, and a feeling of fullness from the carbon dioxide gas released in your stomach.
Daily or prolonged use is a different story. Using Eno every day for weeks can lead to several problems:
- Electrolyte imbalance. The steady intake of sodium bicarbonate can shift your body’s balance of sodium and other minerals, potentially causing fatigue, muscle weakness, or confusion.
- Rebound acid production. When you repeatedly neutralize stomach acid, your body may compensate by producing even more of it, creating a cycle of dependency.
- Disrupted gut bacteria. Changing the pH of your intestines over time can alter the environment your gut bacteria depend on, potentially affecting digestion and nutrient absorption.
- Kidney strain. Excess sodium puts extra work on your kidneys. Over time, this can become a concern, particularly if you already have reduced kidney function.
If you find yourself reaching for Eno daily, that’s a sign the underlying issue needs attention rather than repeated symptom suppression.
How to Use It
The standard method is simple: dissolve one sachet (or one level teaspoon, about 5 grams) in a glass of water and drink it while it’s still fizzing. You can take it before or after meals, depending on when symptoms hit. Most formulations suggest not exceeding a set number of doses in 24 hours, so checking the packaging for your specific product is worthwhile.
Timing matters slightly. Taking Eno on a completely empty stomach means the relief will be short-lived, since there’s no food to slow down new acid production. Taking it shortly after a meal, when acid levels peak, tends to give longer-lasting comfort. Either way, the initial relief kicks in within seconds.