This NHS content is written for people in England. Medicine names, availability, prescribing and services may differ in other countries.
Common side effects
Simeticone is a very safe medicine and is generally not known to cause any side effects.
Serious allergic reactionIn rare cases it's possible to have a serious allergic reaction (anaphylaxis) to simeticone.
Meds New IA (H4) - serious allergic reaction
Call 999 now if:
- your lips, mouth, throat or tongue suddenly become swollen
- you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
- your throat feels tight or you're struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
- you suddenly become very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.
These can be signs of a serious allergic reaction and may need immediate treatment in hospital.
View the original NHS website page ↗. Refreshed 19 August 2026.
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