Horse loosing chunks of hair

Question
I have 12 year old arabian gelding and he loosing massive amounts of hair all of a sudden. These chunks of hair are coming out with crusty seemingly dead skin attatched to it. he seems to have sores but they are kind of dry. Not pussy or bleeding. I have not been riding him so its not from the saddle. It only seems to be on his back right now but he is got what looks like dandruff. Now I have a mare that has been itchy as well, and really dandruffy but she had a huge thick winter coat where as the gelding didn't. I am wondering if one of them didn't pass it on to the other? What does this sound like to you and how can I fix it? I thank you for your time.

Answer
Shirley:

There is no  way I can tell what this is without being able to examine the horses. The condition sounds similar in both horses. They however, did not very likely pass it to one another. As a guess, the condition sounds possibly moere like an infectious condition that occurs due to persistent dampness of the skin and subsequent bacterial infection. If you are concerned about it you need to get a vet to look at it first hand. It may be responsive to something as simple as good currying and a short cource of antibiotics. Also, the horse(s) need to stay dry. The description you provide is very similar to a condition known as "rain rot". If your vet decides this is what it is likely to be, it should be pretty easy to treat. Otherwise, he/she may need to do skin scrapings and maybe even a biopsy of the skin to make a diagnosis and an appropriate treatment plan. Good luck with this. Let me knwo if I can help in any other way.