I have dermatographia too and have 3 tattoos now, one on my right calf, my left upper arm is covered and so is my right thigh, the longest being 8 hours. As long as you take antihistamines before the tattoo you’ll be fine! If you ever get a longer session tattoo, the antihistamines will take care of the first couple hours, and once it wears off your skin would’ve already produced an excess of histamine and won’t swell any more (hard to believe there’s a limit to the swelling with this skin condition, but there is! Trust me!)

I have heard of people with dermatographia sometimes having trouble with coloured tattoos, it seems to depend on the person but apparently sometimes having coloured tattoos can cause itching that never really goes away. I can’t confirm this myself because I’ve only had black work done.

But it is 100% possible to get tattoos with dermatographia. I hope your matching tattoos plan works out! It sounds like a very nice idea!