Suggest Remedy For Rash On Forearm

I have a question about a rash on my forearm. I am a 53 year old woman and a diabetic. I had surgery on Sept. 15th for a broken arm. I had an IV inserted in my outer forearm. On Oct. 22nd I found a red spot about 3” long and ¼” wide on my forearm about ½” away from the IV spot. It looked like blood was just under the surface of the skin. About 1 week later as this spot grew a portion broke open and blood and a clear liquid seeped out. It itched profusely. I put cortisone cream on it to lessen the itching. It dissipated and came back several times. They appear very quickly, within minutes. They are always in smaller spots and no more seepage. I have been to my family Dr. and a dermatologist. The dermatologist said that it was eczema and to put moisturizing cream on it. The spots keep coming back. They fade away in about 1 week. What can they be?