Wounds and cuts heal faster if there is no pressure on them and if they are kept relatively motionless. Movement disrupts the formation of the new blood vessels. Bandages keep the wound clean, keep harmful bacteria out, and maintain moisture to prevent your skin from drying out. Bandages should be changed daily.
You must wait at least eight weeks (56 days) between donations of whole blood and 16 weeks (112 days) between Power Red donations. Platelet apheresis donors may give every 7 days up to 24 times per year. Regulations are different for those giving blood for themselves (autologous donors).
In the United States, you must wait 12 months after getting a tattoo or body piercing before donating blood if your state does not regulate tattoo facilities. This is because bloodborne diseases may be spread by needles, and no one has come up with a good way to vet the tattoo and piercing parlors as not re-using needles.