To protect yourself from HIV, remember to look both ways. You can be hit by HIV through sex or through blood. Even very small amounts of blood – such as might be found on reused needles or razors – could infect you if it could get past your skin.

During medical and cosmetic procedures such as injections, tattooing, or haircuts, instruments such as needles, clippers, or razors may jab or cut someone, and thereby pick up small amounts of their blood. If someone is infected with HIV, a drop of their blood as small as the period at the end of this sentence may have several HIV particles. Any one of these particles could infect you if it could past your skin.

HIV in small amounts of blood can live for some time outside the body. Even after blood dries on a razor, for example, some HIV can live for hours.¹ If blood stays wet – such as in a needle or syringe – HIV can live for weeks.²