The Stain Library

Stain

Period blood stains

A protein stain that lifts out easily in cold water, usually found dried the next morning, and bonded in permanently the moment anything warm reaches it.

  • TypeProtein
  • Heat sets itYes
  • Reviewed1 September 2026

If it has just happened, whatever it is on

Cold water, straight away, and blot rather than rub. Lift anything solid off first with the edge of a spoon, then flush from the back of the fabric until the water runs clear, or blot with cold water on a cloth on anything that cannot be flushed. If you cannot deal with it now, leave the item in cold water rather than letting it dry.

Do not do this

No hot water, no tumble dryer, no iron, no steam and no warm wash until the mark has completely gone. Do not rub, which spreads the mark and pushes it deeper. Do not mix chlorine bleach with vinegar, lemon juice, limescale remover or an ammonia based glass cleaner.

Period blood on specific materials

A period stain is almost always found some hours after it happened, dried and darkened to brown. That sounds worse than it is. Drying is not the same as setting, and a mark that has never been heated will normally soak out.

Heat is the whole problem

The protein in blood coagulates when it is warmed, and a coagulated protein is a tougher structure that grips the fibre it is sitting in. Nothing reverses it. A wash at forty degrees, a spin in the tumble dryer or a pass with an iron will all do it, and so will pouring a kettle over the mark, which is advice that circulates surprisingly widely.

Why time matters less than temperature

A mark that dried on a sheet a week ago has gone out of solution, and cold water plus time brings it back, which is why soaking works. A mark that went through a warm wash yesterday has changed structure, and on some materials that is permanent. So the useful question is never how long it has been there, it is whether anything warm has reached it.

It is not quite the same as a nosebleed

Menstrual fluid carries endometrial tissue and cervical mucus alongside the blood, so there is more solid material to lift off first and a slightly greasy residue that plain water can leave behind. A drop of detergent earns its place even on a fresh mark for that reason. The fluid is also darker from the start and lower in haemoglobin than blood from a cut, which is why it dries brown rather than red.

If the blood is not your own

Blood can carry bloodborne viruses. Where it is someone else's, put on disposable gloves, cover any cut or graze on your hands with a waterproof dressing first, and wash your hands afterwards. That is the standard precaution and it applies to a small mark on a sheet in a shared house.

How period blood behaves

Menstrual fluid is blood plus endometrial tissue, cervical mucus and vaginal secretions, so it carries more solid material and more mucus than blood from a cut. It also leaves the uterus without fibrinogen, which is why it does not clot, and it is darker to start with because it is not freshly oxygenated.

For stain purposes the protein is what decides everything. Warm it and it coagulates, the way an egg white turns solid, and once that has happened inside a fibre or a pore it is bonded there rather than sitting in it.

Related stains

Sources

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

  1. How to remove period blood stains, Bodyform manufacturer

    Manufacturer guidance that hot water is ruled out on a period stain, that the mark is blotted rather than rubbed, that a thirty minute cold soak comes before a gentle detergent wash, that a salt and cold water paste can be left several hours or overnight, and that vinegar, lemon juice and hydrogen peroxide can strip colour from darker bedding so are tested first.

    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 encourages the proteins to set into the fabric, to soak in cold salted water at one or two tablespoons of salt per litre for several hours, to use an enzyme rich biological formula but not on wool or silk, and not to wash hot until the mark has gone.

    Checked 1 September 2026

  3. Detection and comparison of menstrual blood samples, Biomedical Journal of Scientific and Technical Research publication

    Forensic comparison establishing that menstrual blood leaves the uterus in a fluid state, contains no fibrinogen and cannot be made to clot, carries endometrial tissue, vaginal fluid and cervical mucus alongside the blood, and is darker and lower in haemoglobin than peripheral blood at roughly 2 to 4 grams percent against 10 to 15.

    Checked 1 September 2026

  4. 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 protein mark that plain detergent will not shift.

    Checked 1 September 2026

  5. Safe management of blood and body fluid spillages, Infection Prevention Control authority

    Establishes that a disposable apron and gloves are worn for a blood spillage, with facial protection where there is a splash risk, gives household bleach at one part in ten of cold water for a hard surface, and states that chlorine disinfectants must not be used on carpet, soft furnishings or untreated wood because they bleach them.

    Checked 1 September 2026