Blood

If you allow blood spots to set and dry into fabric, they become notoriously hard to remove. Rinse the spot on clothing as quickly as possible in cool water while gently chafing the fabric between your fingers. If this can’t be done right away, blot the spot with a cloth or paper towel moistened with cool water. If you act quickly enough, any remaining shadow or ring likely will disappear once the garment is washed.

 

For set-in blood stains, soak colorfast fabrics in an enzyme cleaner such as Biz or Shout!, and then rinse with water. Use mild laundry detergent on non-colorfast garments.

 

According to the IICRC, blood is a protein spot. "Protein comes from body discharge or foods: for example blood, egg, milk, animal urine or feces. When fresh, much protein, such as blood, is readily soluble in water. But once it ages or is exposed to direct sunlight over time, protein may not be readily water soluble, and it can be quite difficult to remove. It must be broken down into more simple components that can be blotted, extracted or rinsed from fabrics. To make persistent protein spots soluble, enzyme digesters may be required."

 

See also the IICRC / HC Stain Removal Wizard.  

 

Depending on the application process used, spot cleaning upholstery with water or solvents may — or may not — be recommended. To protect any warranty that may be in force, check for a care label underneath the furniture or read any printed instructions that came with the piece. If neither is possible, consult with the retailer who sold the furniture, or check the manufacturer’s website for a section such as “care and maintenance,” which may include helpful tips.

 

Reference:

 

Jeff Bredenberg, editor, in Clean It Fast, Clean It Right: The Ultimate Guide to Making Everything You Own Sparkle & Shine.