I had a visit from my vet yesterday to discuss Sid's mallenders, which have flared up and dropped off during the summer. She was helpful. Her view was:
* Mallenders is indeed hyperkeratosis, and horses are predisposed to it if they have dry skins and coats, as many feathery cobs, heavy horses and Friesians have. In most cases there is a causative factor - something makes the horse's skin overgrow. The problem is that there are very many possible causative factors and combinations of factors, and it is likely that in each horse there is an individual combination of factors: bacterial, fungal, parasitic, metabolic and environmental.
* As a result the only way for a vet to treat them appropriately is to take samples from the scabs, culture them, and create a bespoke medication (usually a cream or liquid) which works against the bacterial, parasitic or fungal factors found in that specific horse. Even this will not address metabolic or environmental factors.
This is very expensive, and since mallenders is not a life threatening or (except in very serious cases) performance threatening condition, vets don't usually suggest it. As a result 99% of owners treat it as a chronic condition which can only be managed, and find the solution that works best for them by trial and error.
As far as Sid's condition went, she said:
* his mallenders is mild;
* I appear to be managing it adequately;
* he allows me to handle his legs, part his feathers, and rub in the horse oil I am using. This is by no means the norm and indicates that he trusts me and that he finds the treatment helpful. He wouldn't let the vet touch his legs below the knee.
Therefore I should continue doing what I am doing. I would do better in treating the condition if I removed the excess skin/scabs and treated with an antibacterial, but this would hurt and sting and, as the vet said, "end up with you on the roof of your stable and Sid up the other end of the field". She thought it wasn't worth the trouble for a mild condition.
She also recommended:
* grow the feathers, as they provide protection
* never wash his feathers unless I absolutely have to (
@Cortrasna, you were right!). If I absolutely have to, use an animal shampoo such as Malaseb, never a human medicated shampoo
* feed a supplement to promote moisture in the skin and coat. She recommended mirra-coat, of which I found possibly the last 2 tubs in the whole of the UK and bought them yesterday. I notice that it contains biotin.
I'm going to copy this into Sid's diary so I have a record of it which I won't forget!