help with swollen line work

i am a professional tattoo artist who has been tattin for 5 years, and i just did 3 custom tattoos on people very close to me and are only outline, each one has completely healed within a week and a half, and then shortly thereafter has swollen on just the linework. one piece which was on my girlfriend was done first and has since flattened out and the other two a on my brother and my close friend and are pretty swollen right now. Two of the pieces are just black outline so that should take allergic reactions outta the picture as well as phototoxic reactions, and the third piece was outlined in blue and purple. i am very perplexed and other tattoos i've done the same days are fine. what could cause this?? the only thing in common between them is that each one was drawn on with sharpie first. i should mention also that i use nuemas, and sanitize with benzylkonium, and did have issues on those days with the needle seating in the back of the tube. maybe i'm overthinking but this has never happened to me and i can't figure out why. p.s. i will update you as time goes on and hopefully they will have settled

Some people do have slight reactions to the ink. If you have done more that just outlines on them, I think it may have raised as well. Time will tell if their body will get accustomed to the ink. Being that you have 4 years and 9 months more experience than I do...I am sure are well aware of peoples reaction to the pigment.

update on the swollen line work, after weeks of research and racking my brain, i have found only one thing in common with each tattoo that had a reaction, and that was that i drew the piece on with a sharpie first. I have since told my clients to put vitamin E on the oultine and keep me posted, within about 2 more weeks the outline have completely flattened out. Now i know that black sharpie has no reactions in skin, and with each piece that had trouble i had used several different colors of sharpie on them, i would have to assume that probably most sharpies are fine on skin but that one color is troublesome, probably the reds, but i don't know for sure. I have since thrown out all my colored sharpie and am going back to a simpler way with just a pen and black sharpie to finalize. Please let me know of your experiences

I just hit up Walmart for 80 packs of Bic markers. 1$ for 10....can not beat that deal. Also, try not using black markers or pens. You may have a tougher time seeing the lines. Also, grab a can of "Spray Stuff". Spray it over your marker lines. It will help hold them longer.