Greasy, scurfy coat - underlying problem or not?

Don't know if this should be here or under grooming.

One of my dogs, who receives the same diet and care as the other two, has a noticeably greasy coat and a serious dandruff problem! The hair seems coarser and shorter, too.
I am trying to treat this from the outside with shampoo from the vet for this purpose but wondered if there might be an underlying cause that would benefit from a supplement such as fish oil?
Does anyone have an experience of a bad coat condition being linked to something else? Strangely, it seems to affect the back of his neck and shoulders only. The only thing that could have caused it externally in that region is when he used to be walked on a choke chain (normal practice in Ireland before anyone remarks on it) which I no longer use. He is otherwise in excellent health.

Hi Deccy the problem could be caused by a number of things..are you using Malaseb wash to treat it? This is good but you do need to leave it on the coat for the required time.

Do you feed fresh veg in the diet? The vitamin C in chopped greens/veg is good for skins. Not sure what you feed but If the skin is greasy more oil in the diet may not help.

I do have some experience of a terrible skin reaction, just after putting some frontline (or whatever it was) onto a dog. That sounds like the region you would put it on as well... have you used anything like this recently which could have led to a reaction?

Unfortunately, Malaseb is not available in ROI even my vet can't get it. I popped round to the surgery and he has given me what he thinks is the next best thing, it's called Sebomild P made by Virbac Animal Health, and is for exactly the condition I am trying to clear. You can use it up to 3 times a week too. I shampooed the lad last night, even managed to keep it on for the required 5 minutes without him leaping out, so we'll see what happens. I have changed the variety of his food to white fish, too.
No, nothing at all, in fact thought I would do him this weekend - first time this year - carefully avoiding the affected area!

Thanks for the suggestions folks, I'll let you know how we get on.

I used sebomild p on syd for the same kind of problem, seems to have cured it. we used it twice a week for about a month then once a week for a further 2 weeks. because his problem was localised just along his back I used to make the area damp and then put diluted shampoo on his back, rub it well in and then leave him either outside or in the conservatory depending on the weather, once the required 10 minutes was up i used to take him up to the bathroom and then shower him all over. Trying to keep them in the bath for 10 minutes just standing or sitting there is asking a bit much of the dog. My way was definately easier.