Eno is an effervescent antacid powder — the “fruit salt” that fizzes when stirred into water. It is taken for heartburn, indigestion, acid reflux and the bloated feeling after a heavy meal. It works within minutes, and it is designed for occasional use rather than daily treatment.
What is Eno?
Eno is sold as a general-sale antacid, not as a scheduled medicine, which is why it sits on supermarket shelves rather than behind a pharmacy counter. It does not appear in the South African Medicine Price Registry, and that is expected for a product of this type.
(A search of that register for “Eno” returns unrelated products whose names merely contain those three letters — penicillin suspensions, phenobarbital, atenolol. None of them is this product. Disregard those matches if you search it yourself.)
Antacid fruit salts of this kind work on simple chemistry. They combine an alkaline carbonate or bicarbonate with a food acid in dry powder form. Nothing happens while the powder is dry. Add water and the two react, releasing carbon dioxide — the fizz — and producing a solution that neutralises stomach acid on contact.
That is the whole mechanism, and it explains both the appeal and the limits:
- It works fast, usually within minutes, because neutralisation is immediate.
- It does not last long, typically an hour or two, because it does nothing to reduce acid production.
- It contains sodium, which is the single most important thing to know about it, and the reason some people should not use it at all.
Read your own pack. Formulations of effervescent antacids differ between brands and countries, and the sodium content and any added ingredients are on the label.
What is Eno commonly used for?
- Heartburn — the burning behind the breastbone when stomach acid rises into the oesophagus.
- Acid indigestion and stomach discomfort after eating.
- A sour or acid taste, and acid regurgitation.
- Bloating and fullness after a large or rich meal.
- Overindulgence, including the stomach discomfort after too much food or alcohol.
- Occasional nausea related to indigestion.
It is for occasional, short-term relief. That is not a marketing caution — it is the honest limit of what a neutralising antacid does. It settles a symptom that is already happening and leaves the cause untouched.
If you find yourself reaching for it most days, that is a signal rather than a habit. Regular heartburn usually responds far better to a medicine that reduces acid production — an H2 blocker such as famotidine, or a proton pump inhibitor such as omeprazole — and it also deserves a look at why it is happening. Persistent reflux can inflame the oesophagus over time, and it is worth diagnosing rather than managing indefinitely from a tin.
How Eno fits into this medicine category
| Group | Examples | How fast, how long |
|---|---|---|
| Effervescent antacids | Eno and similar fruit salts | Minutes; short-lived |
| Tablet and liquid antacids | Aluminium and magnesium salts, calcium carbonate | Minutes; short-lived |
| Alginates | Gaviscon-type products | Form a raft on stomach contents; useful for reflux |
| H2 blockers | Famotidine, cimetidine | An hour or so; lasts many hours |
| Proton pump inhibitors | Omeprazole, lansoprazole | Days to full effect; strongest and longest |
| Antispasmodics | Hyoscine (Hyospasmol) | For cramping, not acid |
| Anti-nausea | Metoclopramide (Adco-Contromet) | Nausea and gut motility |
Antacids are the fastest and the weakest; proton pump inhibitors are the slowest and the strongest. Choosing between them is really a question of whether your problem is an occasional episode or a recurring pattern. See the digestive and stomach medicines hub.
What to check before using Eno
The sodium content is the main issue. Effervescent antacids can contain a substantial amount of sodium per dose, which matters far more than most users realise.
Speak to a pharmacist or doctor before using it if you:
- Have high blood pressure, heart failure, kidney disease or liver disease, or are on a low-salt diet. The sodium load can work directly against your treatment.
- Take diuretics (“water tablets”), blood pressure medicines or lithium. Sodium and antacids can affect how these behave — with lithium in particular, sodium changes can alter blood levels.
- Are pregnant. Heartburn in pregnancy is very common and there are well-established options; ask a pharmacist which is suitable.
- Are treating a child. Follow the age limits on the pack and ask for advice.
- Take other medicines regularly. Antacids reduce the absorption of a long list of them — including some antibiotics (tetracyclines, quinolones), iron, thyroid medicine, and HIV medicines such as dolutegravir. Separate an antacid from other medicines by about two hours, in either direction.
Practical points:
- Dissolve it fully in water and drink it while it is still fizzing.
- Do not take the dry powder, and do not exceed the daily maximum on the pack.
- Do not use it for more than a couple of weeks continuously without advice.
Possible cautions and when to ask a pharmacist or doctor
Occasional use in a healthy adult rarely causes problems beyond burping, bloating or mild stomach discomfort from the released gas.
Regular or excessive use is a different matter. Sustained high intake of sodium bicarbonate-type antacids can cause fluid retention, raised blood pressure, swollen ankles and disturbances of the body’s acid–base balance, and there is a rebound effect in which the stomach responds to repeated neutralisation by producing more acid.
Get emergency help for:
- Chest pain, pressure or tightness, particularly with breathlessness, sweating, nausea, or pain spreading to the arm, neck or jaw. Heart attack pain is frequently mistaken for indigestion, and antacids are frequently taken instead of calling for help. If in any doubt, treat it as cardiac.
- Vomiting blood, or material like coffee grounds.
- Black, tarry stools.
- Severe abdominal pain.
- Difficulty or pain on swallowing, or food sticking.
See a doctor if:
- You need an antacid most days, or for more than two weeks.
- Heartburn wakes you at night, or comes with a persistent cough or hoarseness.
- You have unintentional weight loss, persistent vomiting, or a loss of appetite.
- You are over 45 with new indigestion that has not happened before.
- Symptoms change in character or become more severe.
These are the features that separate ordinary indigestion from something that needs investigating — and an antacid that keeps working just well enough is exactly how such things get overlooked.
Related medicine guides
Frequently asked questions
What is Eno used for? Fast, short-term relief of heartburn, acid indigestion, bloating and stomach discomfort after eating. It is an effervescent antacid.
How quickly does it work? Usually within minutes — it neutralises acid on contact. The effect lasts an hour or two.
Can I take it every day? It is not intended for that. Daily heartburn is better treated with an acid-reducing medicine and deserves a doctor’s assessment.
Is it a medicine? It is a general-sale antacid rather than a scheduled medicine, which is why it is sold outside pharmacies.
Can I take it with high blood pressure? Ask a pharmacist first. Effervescent antacids carry a significant sodium load, which can work against blood pressure treatment.
Can I take it with my other tablets? Separate them by about two hours. Antacids reduce absorption of many medicines, including some antibiotics, iron, thyroid medicine and HIV treatment.
Is it safe in pregnancy? Heartburn is common in pregnancy and treatable, but ask a pharmacist which product suits — sodium content is a consideration.
Why does my heartburn come back worse afterwards? Repeatedly neutralising stomach acid can prompt a rebound increase in acid production. That pattern is a reason to move to a different type of treatment, not to take more.