My AB has this problem they are called pyoma's.
Unfortunately there is no cure but they can be kept under control.

Wash your dogs feet in lukewarm water every time it goes outside for a walk or even in garden.

I use homepathic remedies now from Ainsworth which work better than steroids ever did and are really cheap. It is no cure but certainly clears them up and helps to keep them under control.

As for what causes them it can be a number of reasons:
1] Blocked sweat glands
2]alergic reaction, normally to grass
3]The hairs on the bottom of the feet being pushed into the foot(simular to ingrown hair on us humans)

When really bad I use Hepar Sulphuris 30c 3 a day for 3 days followed by Silicea 30c 3 a day for 5 days.
If it is OK but starts to flair up i use Graphites 30c 3 day for 3 days.

I have had 95% sucess with all Ainsworth remedies and recomend to all to buy there book The animal homepathic prescriber.

As Lel says the food could be causeing the reaction and Ainsworth also said to me that a more natural diet would deffinatley help.
I use Eagle Holistic formulae food now and its great!

I also had a staffy a few years ago that had the same problem and i 1st thought it must be something in the area.He was given steroids by my vet (on them for 4yrs)which eventually gave him liver disease ,i have since found these cantonic steroids are banned for animal use in the usa. I wish i had known about homeopathic remedies then and what i no now.
Hope this helps

Thanks everyone for your replies....

He visited the dermatologist yesterday and she is almost certain that he has an allergy to something he is eating. I have two young children so Buster tends to be fed anything and everything..... he has only to eat the food she gave us, absolutely nothing else. He has a months supply of ABs and some special foot wash.... so heres hoping he feels better soon.