In the right hands eyebrow tattooing can be beautiful. The pain is only slight and most cosmetic tattoo artists use topical anesthetics. Understand that if you have light eyebrows that will always be a problem since the skin is colored beneath them so if the light hairs are dense you may wish to consider dying the brow hairs rather than tattooing. If you decide to have this tattooing, be sure that you fully interview your artist and see many representative pictures of their work. If you don't like their style - don't do it with them - move on. This is your face and it must be respected by the person working on it. Allergic reactions are rare - more problems come from bad work by poorly trained artists. Understand that brow color does fade and you will need to have those touched up every few years.