Like all medicines, mometasone can cause side effects, although not everyone gets them.
When you take mometasone using an inhaler, very little medicine gets into the rest of your body, so it's unlikely to give you side effects.
If you're on high doses of mometasone, or you're also taking other steroid medicines or tablets for fungal infections or HIV, you may get underactive adrenal glands (adrenal insufficiency) as a side effect. Ask your doctor if you need to carry a red steroid emergency card.
Common side effects
These common side effects of mometasone inhalers may happen in more than 1 in 100 people. There are things you can do to help cope with them:
Sore throat or hoarse voice
Try rinsing your mouth with water or brushing your teeth after using your inhaler to stop this happening. See your doctor if it does not improve.
Oral thrush (mouth thrush)
Oral thrush is a fungal infection that causes white patches, redness and soreness in your mouth.
Try rinsing your mouth with water or brushing your teeth after using your inhaler to stop this happening.
If you get oral thrush, ask a pharmacist to recommend a treatment such as a mouth gel and get them to check that you're using your inhaler correctly. They may suggest that you see your doctor to discuss the best treatment.
Headaches
Make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Ask your pharmacist to recommend a painkiller. Talk to your doctor if the headaches are severe or do not go away.
Keep using your inhaler but talk to your doctor if the advice on how to cope does not help and these side effects bother you or do not go away.
Serious side effects
It's unusual to have any serious side effects when using a mometasone inhaler.
You're more likely to get serious side effects if you're on a high dose of mometasone for a long time (more than a few months).
Speak to a doctor if you get "moon face" (a puffy, rounded face), and weight gain in your upper back or belly. This happens gradually and can be a sign of Cushing's syndrome.
Call your doctor or call 111 straight away if you get:
- a high temperature, chills, a very sore throat, ear or sinus pain, a cough, coughing up more mucus (phlegm) or a change in colour of your mucus, pain when you pee, mouth sores or a wound that will not heal – these can be signs of an infection
- a very upset stomach or you're being sick (vomiting), feeling very dizzy or passing out, muscle weakness, feeling very tired, mood changes, loss of appetite and weight loss – these can be signs of adrenal gland problems
- changes in your eyesight, such as blurred vision or a cloudy lens in the eye – these can be signs of increased pressure in your eyes (glaucoma) or a cataract
Serious allergic reaction
It happens rarely but it's possible to have a serious allergic reaction (anaphylaxis) to mometasone.
This is different to an asthma attack. If you or your child have asthma symptoms, such as wheezing or tightness in the chest or throat, use a reliever inhaler. If the symptoms do not improve or get worse, call 999.
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.
Children and teenagers
Taking mometasone at high doses for a long time can slow down the normal growth of children and teenagers but the risk of this happening is very low. Talk to your doctor if you're worried. They'll be able to explain the benefits and risks of giving your child mometasone.
Your child's doctor will monitor their height and weight carefully for as long as they're taking this medicine. This will help them spot any slowing down of your child's growth and change their treatment if needed.
Even if your child's growth slows down for a while, it does not seem to have much effect on their eventual adult height.
Your child's doctor or nurse will always aim to give them the lowest dose of steroid medicine to control their symptoms. They'll only be given higher doses if they need extra help for their symptoms.
It's important to remember that inhaled steroid medicines are one of the best ways to treat asthma and reduce the risk of symptoms and asthma attacks.
Other side effects
These are not all the side effects of mometasone inhalers. For a full list see the leaflet inside your medicines packet.
You can report any suspected side effect using the Yellow Card safety scheme.