Hello and welcome to HCM, An rash within five days of getting a tattoo suggests an allergic reaction. The allergic reaction can be against the dye used for the tattoo. If the tattooing needle is not sterile, infection can also occur after injecting the dye. However, you are having a rash after injecting the dye, it is most probably an allergic reaction. you can take an anti-histaminic for the rash and to control symptoms like itching, etc. Of the symptoms persist for a long period of time or increases despite taking medication, you need to visit your doctor. Thanks and take care. Dr Shailja P Wahal