Like all medicines, erythromycin can cause side effects, although not everyone gets them.
Common side effects
These common side effects of erythromycin happen in more than 1 in 100 people. There are things you can do to help cope with them:
Feeling sick (nausea)
Stick to simple meals and do not eat rich or spicy food while you're taking this medicine. It might help to take your erythromycin with a meal or snack.
Being sick (vomiting)
Take small, frequent sips of fluids, such as water or squash to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee. Do not take any other medicines without speaking to a pharmacist or doctor .
If you take the combined contraceptive pill or the progestogen-only pill and erythromycin makes you sick (vomit), your contraception may not protect you from pregnancy. Check the pill packet to find out what to do.
Diarrhoea
Drink lots of fluids, such as water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
If you take the combined contraceptive pill or the progestogen-only pill and you have severe diarrhoea for more than 24 hours, your contraception may not protect you from pregnancy. Check the pill packet for advice.
Stomach cramps
Try to rest and relax. It can help to eat and drink slowly and have smaller, more frequent meals. Putting a heat pad or covered hot water bottle on your stomach may also help. If you are in a lot of pain, speak to your pharmacist or doctor.
Loss of appetite
Eat when you would usually expect to be hungry. If it helps, eat smaller meals more often than usual. Snack when you're hungry.
Bloating and indigestion
Try not to eat foods that cause farting (flatulence), like lentils, peas, beans and onions. Eat smaller meals, eat and drink slowly, and exercise regularly. Pharmacy medicines, like simeticone, can also help.
Serious side effects
Serious side effects are rare and happen in less than 1 in 1,000 people.
Call 111 or a doctor for advice straight away if you get:
- a skin rash
- severe stomach pain – this can be a sign of pancreas problems
- yellowing of whites of the eyes or the skin (although this may be more difficult to see on brown and black skin), or pale poo with dark pee – these can be signs of liver or gallbladder problems
- seeing or hearing things that are not there (hallucinations)
- ringing in the ears, temporary hearing loss, or feeling unsteady on your feet
- a high temperature
Immediate action required: Call 999 or go to A&E if:
- you or your child has had a seizure or fit
Immediate action required: Call 999 now:
- if you have chest pains or your heart is beating abnormally
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to erythromycin.
Immediate action required: 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.
Other side effects
These are not all the side effects of erythromycin. For a full list, see the leaflet inside your medicine packet.
You can report any suspected side effect using the Yellow Card safety scheme.