Scab on head of my cocker spaniel

Question
My cocker had a bad allergy problem and would get lots of flaky scabs on her skin but recently she's been doing good. Now we found this big scab on her head and when we cut the hair around it and tried to cut at it it looked to be a scab and was also flaky.  Does this sound like allergy or some worse skin problem or even cancerous?

Answer
First of all, Brian...tell me what she was allergic to and what was done about that?  Meds?  Food change?  Topical approaches as in medicated shampoo?  How did your vet "decide" it was an allergy?

Did your vet check her thyroid?  How old is she?
What are you feeding her?

Where are you weather-wise where you live and did the skin issues arise in the Spring?

And don't worry...the chances this is cancer or something equally dire is less than zero.
Flaky scabs usually (in cockers) indicate seborrhea
so I need to know what your vet did and why he/she thought it was an allergy.  And was there any infection?

My experience is that family vets know zip about skin conditions and usually hand out steroids.
Delores