black dotted rash

Question
I have a dog that is 1/2 Chinese Crested- Powderpuff and 1/2 Cocker Spaniel.  She was scratching and shedding.  I went to the local pet store and asked what kinds of remedies they had and they suggested a dietary suppliment called The Missing Link by Designing Health, Inc. Omega 3 Basic.  The pet store owner suggested doubling the dose for the first week.  I did that and then went to the regular dose for about 4 days.  The dog (Sophie) stopped shedding so much but now has a rash the she is scratching.  I don't think the rash was there to begin with but I'm not positive.    
The rash is black dotted and seems to almost be some type of scab as it is comming off as she scratches it and is trapped in her fur.  Do you have an idea what this rash may be and/or a treatment for it?
Thanks,
Joy

Answer
Omege 3 fatty acids take 30-60 days to work to stop itching and scratching.  They do not have any antibacterial effect, so if there are black crusty spots, that may be a bacterial infection on the skin.  That needs to be treated with antibacterial shampoo and possibly an antibiotic.  Check with your vet.