Rinse immediately under cold running water — never hot — then soak in Sil 1 für Alles Fleckensalz dissolved in cold water for 30–60 minutes. Blood contains haemoglobin protein that denatures (cooks) above 40 °C, becoming permanently insoluble. Cold water keeps it dissolvable. Sil (Stiftung Warentest Grade 2.4) contains protease enzymes that break haemoglobin into water-soluble fragments, plus oxygen bleach to lift the iron-based red pigment [S1]. Even dried blood responds to extended enzyme soaking [S2].
How to Remove Blood Stains from Cotton
🏆 Based on Stiftung Warentest 2024 testing [S1]
Step-by-Step: Remove Blood from Cotton
- Rinse immediately with cold water (0–3 min). Hold the stain under cold running water from the back of the fabric. The cold water dissolves fresh haemoglobin on contact — you'll see the blood stream away in reddish-pink water. Continue until the water runs mostly clear. This single step can remove 90% of a fresh blood stain.
- Soak in cold Sil solution (30–60 min). Dissolve 1–2 tablespoons of Sil 1 für Alles in 2 litres of cold water (20 °C or below). Submerge the stained area and soak. The protease enzymes work at cool temperatures to digest the remaining haemoglobin protein. For dried blood, soak 2–4 hours.
- Gently work the stain (2–3 min). After soaking, gently rub the fabric against itself under cold water. Loosened blood should lift away. For stubborn dried stains, use a soft-bristle brush with gentle circular motions. Don't use force — let the enzymes do the work.
- Machine wash cold (30 °C). Wash on a normal cotton cycle at 30 °C. You can add an extra dose of Sil to the wash drum for additional enzyme action. Avoid warm or hot wash settings — even 40 °C risks partially setting any remaining haemoglobin.
- Inspect while damp — before drying. Check the stain area on the wet fabric. If any pink or brown shadow remains, repeat the cold soak. Never put a blood-stained garment in the dryer or on a radiator. Heat permanently denatures any remaining protein, making it unremovable.
Test Winner
Sil 1 für Alles Fleckensalz
Grade 2.4Why Sil Works for Blood on Cotton
Blood stains are fundamentally a protein stain — haemoglobin, the oxygen-carrying protein in red blood cells, is what binds to cotton fibres and creates the characteristic red-brown colour. Sil 1 für Alles attacks blood through two complementary mechanisms: protease enzymes that cleave haemoglobin's peptide bonds, fragmenting the large, insoluble protein into small, water-soluble amino acid chains; and sodium percarbonate oxygen bleach that oxidises the iron-based haem group responsible for the red-brown colour [S1]. This dual approach — protein digestion plus colour oxidation — is why Sil outperforms single-action products. The protease enzymes remain active at low temperatures (effective even at 20 °C), which is critical because blood requires cold-water treatment. Many competing products rely on oxygen bleach alone, which works poorly in cold water [S2].
Blood-specific dosage: 1–2 tablespoons per 2 L cold water (20 °C). Soak 30–60 min for fresh blood, 2–4 hours for dried. Never use warm water — it denatures the very protein the enzymes need to break down.
What NOT to Do
- NEVER use hot or warm water. This is the #1 mistake. Haemoglobin denatures above 40 °C — the protein coagulates and bonds permanently to cotton cellulose, just like a cooked egg white becomes solid. Once heat-set, blood stains are essentially permanent.
- Don't tumble dry before the stain is gone. Dryer temperatures (60–80 °C) will permanently set any remaining blood protein. Always air dry and inspect first.
- Don't use chlorine bleach on coloured cotton. Chlorine can react with haemoglobin's iron to create rust-like discolouration — a green-brown tint worse than the original stain.
- Don't rub aggressively. Blood that has begun to dry can be pushed deeper into cotton's open weave structure. Soak first, then gently work.
- Don't wait. Fresh blood dissolves in cold water almost instantly. After 24 hours of drying, the haemoglobin partially denatures and treatment time increases 5-fold.
Fabric-Specific Notes for Cotton
Cotton is absorbent but responsive. Blood penetrates cotton's open cellulose structure deeply, but the same absorbency that makes it vulnerable also makes it responsive to treatment — cotton readily absorbs the enzyme solution, carrying it deep into the fibre where the blood has gone. White cotton can tolerate stronger Sil concentrations (2 tablespoons per litre). Coloured cotton should be tested on an inside seam first, though Sil is generally colour-safe at recommended concentrations.
Frequently Asked Questions
Can you remove dried blood stains from cotton?
Yes, though it takes longer. Soak in cold water for 30 minutes to rehydrate the haemoglobin, then apply Sil and soak for 2–4 hours. The protease enzymes break down denatured blood protein. Multiple cycles may be needed for old stains.
Why does hot water set blood stains?
Blood contains haemoglobin protein that denatures above 40 °C — the same process that turns egg white opaque when cooked. Once denatured, the protein becomes insoluble and bonds permanently to cotton fibres. Always use cold water.
Does hydrogen peroxide remove blood from cotton?
It can help on white cotton but may bleach coloured fabrics and weaken fibres. Sil provides similar oxidising power with better fabric safety and the added benefit of protease enzymes.
Can you remove period blood stains from cotton underwear?
Yes. Rinse in cold water, then soak in Sil solution. Keep water below 30 °C to protect elastic components. Sil's enzymes are effective on the specific haemoglobin proteins in menstrual blood.
Does salt remove blood stains from cotton?
Salt water helps with fresh blood through osmotic action, but it's only partially effective and doesn't work on dried stains. Sil's enzymes actively break down the blood protein rather than just drawing it out.
Sources: [S1] Stiftung Warentest, Fleckenentferner-Test 2024, Grade 2.4 (GUT) for Sil 1 für Alles Fleckensalz. [S2] International Journal of Biological Macromolecules, "Protease-mediated degradation of haemoglobin adsorbed on cellulose fibres," vol. 178, 2021.