This information is for parents of a child who has asthma. It tells you about sodium cromoglicate from an inhaler, a treatment used to prevent asthma symptoms. It is based on the best and most up-to-date research.
Does it work?
Not very well. The research on sodium cromoglicate has found that it doesn't help children with asthma, or only helps a small amount. Steroids from an inhaler are usually a better treatment for preventing asthma. Your child's doctor may recommend sodium cromoglicate if steroids don't help or aren't suitable for some reason.
What is it?
Sodium cromoglicate is an anti-inflammatory medicine that is breathed in through an inhaler to help keep asthma symptoms at bay. Its job is to prevent the swelling (inflammation) in the airways to keep asthma under long-term control. It isn't designed to treat an asthma attack.
Your doctor or nurse may refer to this medicine as a preventer. One brand is Intal.
Breathing in sodium cromoglicate is a good way to take the drug, as it gets straight to the lungs, where it's needed. Sodium cromoglicate comes in a dry powder inhaler called a Spinhaler.
Sodium cromoglicate is generally prescribed for children with relatively mild asthma. Your doctor may suggest trying this treatment if your child needs their quick-relief inhaler more than once a day. But your doctor will probably recommend that your child tries steroids from an inhaler first. 
How can it help?
If your child gets asthma symptoms often, a sodium cromoglicate inhaler might improve their symptoms a little. 
Most children find that steroid inhalers work better than sodium cromoglicate inhalers.
How does it work?
Sodium cromoglicate seems to calm down and prevent swollen airways, making it easier for your child to breathe and less likely that he or she will react to asthma triggers (such as house dust mites and smoke).
Experts are not exactly sure how sodium cromoglicate works. They think that it probably stabilises the outer layer of cells, called mast cells, in the lining of the airways. This stops them from releasing the chemicals that cause inflammation.
Can it be harmful?
Not many children in the studies got side effects. And the side effects children did get weren't usually serious. They included coughing, a bad taste in the mouth, irritation around the mouth, and a sore throat.
How good is the research on sodium cromoglicate from an inhaler to prevent asthma symptoms?
The research on sodium cromoglicate is mixed.  Some research says it doesn't help any more than a pretend treatment (a placebo). Some says that it only helps a little bit. There's reasonably good research showing that sodium cromoglicate does not work as well as steroids from an inhaler at preventing asthma symptoms.