blisterd tatoo

i have had a tatoo done a year ago on my wrist an the last couple of weeks it swelled up an now gone into a blister it really itchy to the point were i want to cratch it out its so sore but the other thing is its not the whole tatoo its just the red love hearts that i have on it i did ask the tatoo guy that done it he just said some of his do it an that was it i have 6 other tatoos an they have never had any problems with them. any advice on wat it can be because its really driving me mad now.

Some reds contain iron, some contain toxic metals such as cadmium or mercury. There is an organic red that causes fewer reactions than the metal-based reds. Red ink is well-known for causing sensitivity reactions. The more dilute the pigment, like in orange or pink, the lower the chance of a reaction, but I would say the risk is still present.