Infections
Infections are generally marked with redness in the early stages. Usually the red area will produce more heat than the surrounding areas. Later stages include swelling, discharge, and/or necrosis.
Infections do not always occur from any unclean practices. Sometimes your body's defenses are let down when using the wrong lotion/ointment for your skin, or chafing and irritation due to contact with clothes, objects you work with, especially in manual labor.
For instance an infection is more likely to manifest in a motorcyclists gloved hand, than if he were to refrain from riding for a few days. Or a SCUBA diver with a back tattoo, a wetsuit, and 50lbs. of equipment strapped to his back.
Bacterial Infections are usually treated successfully with antibiotics. Only in the worst cases of strep and staph are you going to lose some deep tissue. Viral Infections are less apparent, and generally do not appear on the surface of the skin (except in cases like herpes)
The only way to kill a virus is to kill the host, so be sure your tattooist is up to date on all health and safety techniques, and has had some training in such techniques.
How do I treat an infection?
I don't like to give medical advice, but there are some measures you can take if you are uninsured and a doctor is a last resort. The first thing you want to do is let the tattoo dry out. The drying causes scabbing sometimes, but moisture gives an infection a perfect environment to keep breeding. DO NOT under any circumstance use an antibiotic ointment. If you have an infection, it is too late for neosporin. Products like that are for prevention, not as medicine. The next step is to cleanse your infection at least 3x a day with a good antibacterial soap, drying the tattoo with a paper towel after each washing. Surgical soaps work very well, but stay away from any form of Iodine as it may discolor your tattoo, and peroxide will eat the tissue that is trying to heal. My recommendations are Hibiclens Surgical Soap, Basic H (if it still exists) or Bactine.
If your infection worsens, see a doctor immediately. If you feel any signs of weakness, or fever, your condition may worsen very quickly. This advice applies to only superficial, manageable infections.