This information is for people who have hay fever. It tells you about steroid nasal sprays, a treatment used for hay fever. It is based on the best and most up-to-date research.
Do they work?
Yes. Steroid nasal sprays can help with symptoms that affect your nose, such as sneezing or a runny, itchy, or blocked nose. But they don't seem to help with red or watery eyes.
What are they?
The steroids used to treat hay fever are called corticosteroids. They help calm your body's allergic reaction to pollen. They're similar to the natural steroids your body makes. They're not the same as the anabolic steroids that some athletes and bodybuilders use.
You can buy some steroid nasal sprays over the counter at a pharmacy. For others you'll need a prescription from your doctor. There are several different corticosteroids. Some common ones (with their brand names) are:
You breathe these sprays in through your nose once or twice a day. They seem to work best if you start using them about two weeks before you expect to get hay fever symptoms.  If you already have symptoms, you'll need to use the spray for a few days before it helps.
If you have more severe or longer-lasting hay fever, your doctor may suggest you use a steroid spray together with antihistamine tablets.
How can they help?
There's lots of research saying that steroid nasal sprays help with hay fever.  They reduce the symptoms that affect your nose but don't seem to work for red or watery eyes.
Steroid sprays may work better than antihistamine sprays or tablets for symptoms that affect your nose.   Steroid sprays also work better than drugs called leukotriene blockers. But taking antihistamine tablets together with pseudoephedrine or a leukotriene blocker may help them work just as well as steroid sprays.
All the different steroid sprays seem to work about the same as each other.  There's been lots of research comparing steroid sprays, but most of the studies found that there wasn't any difference between them.
How do they work?
Hay fever is an allergy. Allergies happen when your immune system overreacts to something that's harmless for most people. If you have hay fever, your body overreacts to pollen in the air. Using a steroid spray helps to reduce your body's allergic reaction to pollen.
Can they be harmful?
Steroid nasal sprays can cause side effects, but they're usually mild. Some people get nosebleeds or irritation inside their nose. 
It's possible for steroid sprays to damage your septum. That's the hard tissue that runs down the middle of your nose, between your nostrils. But this is extremely rare.