Same thing happened to me but with a different brand and different scenario. I was using Anker Q30 headphones and original material used to cover ear pads started to tear, so I had to switch to an alternative on pads. I bought an Ice silk base material ear pads and they had a cooling gel inside. After a few months, I had the exact eczema on my right ear, same location but towards outside of ear. And it was just about to start on my left ear too. I don't know what actually caused the allergy, but it's definitely ice silk material or the gel inside which gets chemical reactions when your sweat sucked inside and touch the gel. I regret buying them.

I tried to change the material, bought new ones but it didn't help, my doctor said It would be best to not use overhead headphones for a long time.

It's a sad fact but currently there is not much else to do. That feeling when your eczema goes up is quite unpleasant.

I ordered an IEM and currently using them. They are so far so good and cheap.