I would also check the skin around the hematoma(s) for signs of irritation--obvious fly bites, dandruff, hair loss, etc. It could be irritation from allergies, mites/ticks, stuck on dirt...She could be kicking up any number of things. I'd also suggest washing the area with Ivory (or like gentle soap) before you do anything. If it's skin related, you might consider applying some M-T-G to the skin (not on the hematomas; you don't want the DMSO mixing or potentially reacting with the M-T-G). Some horses with sensitive skin react to M-T-G (we have an arab at the barn who gets welts from it and most conditioners/treatments), so be sure to test it on a small spot of hair elsewhere a day or two before you apply it to the affected area.