Body substance isolation is a practice of isolating all body substances (blood, urine, feces, tears, etc.) of individuals undergoing medical treatment, particularly emergency medical treatment of those who might be infected with illnesses such as HIV, or hepatitis so as to reduce as much as possible the chances of transmitting these illnesses.^[1] BSI is similar in nature to universal precautions, but goes further in isolating workers from pathogens, including substances now known to carry HIV.

Practice of Universal precautions was introduced in 1985–88.^[2][3] In 1987, the practice of Universal precautions was adjusted by a set of rules known as body substance isolation. In 1996, both practices were replaced by the latest approach known as standard precautions (health care). Nowadays and in isolation, practice of body substance isolation has just historical significance.^{[citation needed]}

Body substance isolation went further than universal precautions in isolating workers from pathogens, including substances now currently known to carry HIV. These pathogens fall into two broad categories, bloodborne (carried in the body fluids) and airborne. The practice of BSI was common in Pre-Hospital care and emergency medical services due to the often unknown nature of the patient and his/her disease or medical conditions. It was a part of the National Standards Curriculum for Prehospital Providers and Firefighters.Types of body substance isolation included:^{[citation needed]}

• Hospital gowns
• Medical gloves
• Shoe covers
• Surgical mask or N95 Respirator
• Safety Glasses

It was postulated that BSI precautions should be practiced in environment where treaters were exposed to bodily fluids, such as:

• blood, semen, preseminal fluid, vaginal secretions, synovial fluid, amniotic fluid, cerebrospinal fluid, pleural fluid, peritoneal fluid, marrow, pericardial fluid, feces, nasal secretions, urine, vomitus, sputum, mucus, cervical mucus, phlegm, saliva, breastmilk, colostrum, and secretions and blood from the umbilical cord^[1]

Such infection control techniques that were recommended following the AIDS outbreak in the 1980s. Every patient was treated as if infected and therefore precautions were taken to minimize risk. Other conditions which called for minimizing risks with BSI:

• Diseases with air-borne transmission (e.g., tuberculosis)
• Diseases with droplet transmission (e.g., mumps, rubella, influenza, pertussis)
• Transmission by direct or indirect contact with dried skin (e.g., colonisation with MRSA) or contaminated surfaces
• Prion diseases (e.g., Creutzfeldt–Jakob disease)

or any combination of the above.

• Barrier nursing