The Stain Library

Cleaner

Biological laundry detergent

Ordinary washing detergent with enzymes added, and the one household product that breaks protein apart rather than washing round it.

  • TypeEnzymatic
  • pHMildly alkaline, which is the range the enzymes work in
  • Reviewed1 September 2026

Safety

Rinse it out of anything that will touch skin for long periods. Enzyme residue left in fabric is a common cause of irritation, and bedding is the usual culprit because it is worn against the skin all night.

How to use it

For a blood mark, work a little of the liquid into the wet fabric and leave it on for fifteen to thirty minutes before rinsing cold. It needs time and moisture, not heat.

Enzymes work in cool and warm water alike, so there is no reason to raise the temperature for them, and every reason not to while a blood mark is still there. Powders often carry an oxygen bleach as well as enzymes, which is useful on white cotton and worth avoiding on anything dark until it has been tested.

Which materials it is safe on

  • Finished leather No, not recommended

    Leather is protein. A protease is designed to break protein down, and the finish and the hide are both at risk. The leather trade body rules out detergents on finished leather in any case.

  • Fabric sofa Only with caution

    Only on a W or WS coded fabric, and only as a trace on a damp cloth, because there is no way to rinse upholstery properly. Never on S or X coded fabric.

    Use Washing up liquid instead.

  • Synthetic carpet Only with caution

    The fibre tolerates it, but a laundry detergent cannot be rinsed out of a carpet, and residue left in the pile attracts soil. Use a carpet or upholstery spotter instead where one is available.

    Use Washing up liquid instead.

  • Bed sheets Yes, safe

    Safe on cotton and polycotton bedding. Rinse it out properly, because enzyme residue in something slept in is a common cause of skin irritation.

  • Cotton Yes, safe

    Cotton is cellulose, and a protease has nothing to act on in it. This is the standard treatment for protein marks on washable cotton.

Which stains it actually shifts

  • Blood Yes, it works

    Protease breaks the peptide bonds in the haemoglobin and plasma proteins, which is the only household route that works on blood that has already dried into the fibre.

A biological detergent is an ordinary detergent with enzymes blended in. The enzyme that matters for blood is protease.

What a protease actually does

Protein is a long chain of amino acids held together by peptide bonds. A protease hydrolyses those bonds, cutting the chain into short fragments that dissolve and rinse away. Nothing else in a normal cupboard does that.

Why it is the answer for dried blood specifically

Cold water lifts blood that is still soluble. Once the protein has dried or coagulated it is no longer soluble, and the only routes left are to break it up chemically or to oxidise it. Protease is the gentler of the two, and it is safe on colours in a way that bleaching is not.

Sources

What we checked and when. Where a manufacturer instruction disagrees with anything here, follow the manufacturer.

  1. Enzymes in laundry detergents, University of Maryland publication

    Explains that proteases hydrolyse the peptide bonds holding a protein together, which is the mechanism a biological detergent uses on a blood mark that plain detergent will not shift.

    Checked 1 September 2026

  2. Persil UK, how to remove blood stains from clothes manufacturer

    Manufacturer instruction to use cold water only because hot water sets the proteins, to soak in cold salted water at one or two tablespoons of salt per litre for several hours, and not to wash hot until the mark has gone.

    Checked 1 September 2026

  3. Getting blood out of bedding, Mumsnet housekeeping discussion community

    A long UK thread in which an overnight cold soak, cold salted water and a biological pre-soak are repeatedly reported as what worked, and in which the original difficulty was a hot wash that had already set the mark.

    Checked 1 September 2026