Unfortunately, there are many conditions that can cause a dog to experience hair loss including ringworm, mange, hypothyroidism, cushing disease and allergies. While it sounds like this might be ringworm based on your description, Staffys are prone to demodectic mange and allergies.
Ringworm can have a scaly reddish rash around the edges of the bare patches though there can be a rash in the bare area as well. Any over the counter antifungal cream for ringworm will work on this. The cream should be applied to an area slightly larger and for about a week after it appears to have cleared up. There are two types of mange and mange is actually caused by mites. Usually hair loss starts in specific areas of the body before spreading to other areas. Allergies are a frequent cause of scratching and hair loss and an be caused by many different things. Treating any problem without knowing for sure what it is causes a delay in the treatment of the real problem if your first guess is wrong. I really suggest you have your Vet examine the areas and diagnose this. Below are websites that will go into more detail on these conditions.
Here is a website on Ringworm:http://www.marvistavet.com/html/body_ringworm.html
Here is two on Mange.http://www.marvistavet.com/html/body_demodectic_mange.html http://www.marvistavet.com/html/body_sarcoptic_mange.html
Hypothyroidism and cushing on these pages:http://www.petplace.com/dogs/hypothyroidism-in-dogs/page1.aspx http://www.petplace.com/dogs/hyperadrenocorticism-cushing-s-syndrome-in-dogs/page1.aspx
You can read up on allergies here:http://www.nhahonline.vetsuite.com/Templates/ContentPages/Articles/ViewArticleContent.aspx?Id=864 http://www.lbah.com/allergy.htm
If you suspect an allergy condition is to blame, you can give your dog Benadryl up to 2mg per pound every 8 hours.
There might be a secondary skin condition in addition to the allergy such as staph dermatitis or yeast dermatitis. Staph usually occurs on the lower regions of your pet and tends to have small pimple type bumps. Shampoo containing Chlorhexiderm and/or Oatmeal can help with this condition though it does not cure the allergy. Yeast typically shows as a greasy area that has a sweet musty odor. Sometimes the skin can become inflamed, darker and thickened due to itching. Yeast likes areas such as between toes, armpits and ears. Selsun Blue Shampoo can help with Yeast dermatitis. When shampooing, lather and leave on 15 minutes before rinsing. These shampoos are not meant to be a cure, just a relief until your pet can see a Vet.
There is also a condition called alopecia which is basically hair loss. You can read all about it in this article: http://www.dvmnewsmagazine.com/dvm/article/articleDetail.jsp?id=7250
Some treatment methods for this are discussed on the following site. You might want to discuss this possibility with your vet. http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2004&PID=8629&O=Generic
I hope this information is helpful.
I believe customers are offered a choice of experts during the submission process. If a vet is not specifically asked for, the question is directed to all experts. I have worked for 10+ years as a vet assistant and have worked with dogs for 16+ years. Ringworm does usually have some redness around the bald area though in many cases it is hidden under the hair around the edges so you do want to check to be sure. The center of the area is usually clear but sometimes will have a rash. Your vet can diagnose this quickly with an in person exam.
To definitely rule out mites, it does require a skin scraping. I have dealt with many animals with mange mites. The kind that usually affects puppies and im many cases starts on the ears, around the eyes and muzzle is demodectic mange which is not contagious. It is believed to be due to a lowered or immature immune system. Staffys are prone to this condition. Ivermectin is one treatment for this but should not be used on herding breeds or mixed dogs that are part collie or hearding breeds. You can read about ivermectin usage and dosages here:
http://www.petplace.com/drug-library/ivermectin-ivomec-heartgard/page1.aspx And about toxicity here: http://www.petplace.com/dogs/ivermectin-toxicity/page1.aspx
No one can give you a definite answer as a skin scraping is necessary to rule out mange mites and a special light is used to diagnose ringworm. Once those possiblities are ruled out, then the vet will treat for dermatitis possibly related to allergies in most casese.