Savas is right. Steroids are a "band-aid" treatment. They work temporarily, but only because they set up a false immune system for the body. Once they start to wear off and the body's own immune system kicks back in, the allergies are back in force because the animal's own immune system can't deal with them. Also, while cats tolerate steroids a LOT better than dogs do, eventually they will probably cause diabetes and a host of other problems. So as big of a pain as it is, it's far better to use a process of elimination method to determine what the cause(s) of the allergies is/are and attack it from that standpoint.
What type of allergies does your cat have? Is it food allergies or respiratory problems or some other type?
Ghilly
The problem with steroidal treatments is they're a good temporary fix but animals tend to build a resistance to them in the long run. Plus, there are negative long term side effects to continual usage.
Now, yes, garlic is a traditional treatment for cats and dogs for ticks and fleas. But there are some suggestive studies that use of garlic in cats can lead to possible blood clotting issues, so I'd advise against using it unless absolutely neccessary.
I would suggest switching to a wheat/ soy/ grain free diet. Use a digestive enzyme. This could help with your cat's breath and allergies.
As a good alternate treatment for the allergies, you can try using a yucca extract product, it can work wonders. Yucca has natural anti-inflammatory properties that can definitely help.
Otherwise, just be careful in researching your products. Modern/homeopathic work very well together. The problem is sometimes the two schools will disagree for various reasons, which is why it's up to you to do your best to do the research, be informed, and make the best decisions for your pet.
What kind of allergies does your cat have? If she's allergic to food, you may want to try a natural diet. It's a hassle to deal with raw meat but it pays off, there are recipes for that online. You can make a whole batch and freeze the rest and feed it to her gradually. It's also cheaper than buying cat food. If it's not food allergies, you may want to try a natural(raw) diet anyway- it will raise her immunity and perhaps relieve her allergies.