Can I pour 3% hydrogen peroxide on wool the way I do on cotton?

No. Peroxide can bleach wool dye and weaken keratin. Stay with cold salt water and mild dish soap. If a shadow remains, take the knit to a cleaner instead of oxidizing it at home.

How do I lift dried blood that has already stiffened on a wool sweater?

Rehydrate the crust with repeated cold salt-water dabs for 20 to 30 minutes before adding dish soap. Do not soak and agitate a whole knit unless the label allows a still, cool hand wash.

Guide

How to Remove Blood Stains from Wool Clothing

Blot with a dry cloth, then dab cold salt water and a drop of mild dish soap. Never use warm water, enzyme detergent, or the cotton peroxide method. Rinse with cool water, roll in a towel, and lay the knit flat to dry.

Wool clothing Blood stain

Context

Conditions that change the method

Delicate surface — Hot water and friction felt wool permanently. Stay with cool water and straight-down blotting.
Color-sensitive — Skip hydrogen peroxide on dyed or dark wool. It can bleach keratin and shift the dye.

Keep blood cold, and do not treat wool like cotton

Heat cooks hemoglobin into the fiber. Protease enzymes digest wool protein the same way they digest blood. Wear gloves if the blood is not yours. If soap or salt water gets in your eyes or on irritated skin, or you feel unsure or uncomfortable, rinse with cool water and get medical advice.

What you need

Cold tap water
Table salt
Mild dish soap (not a biological enzyme detergent)
Clean white microfiber cloths or towels

Blot fresh blood with a dry white cloth, pressing straight down. Then dab the mark with a cloth wet with cold water only. Do not rinse under a hot tap.
Read the care label. If it says dry-clean only, stop after the cold blot and take the garment in. Hand-wash or wool-cycle knits can continue.
Stir 1 tablespoon of table salt into 1 cup of cold water. Dab from the outer ring inward so the salt water loosens hemoglobin without spreading it.
Put one drop of mild dish soap on the remaining mark and fingertip-dab for about a minute. Do not use enzyme laundry detergent.
Dab with a cloth dipped in plain cold water until the soap and any pink tint are gone.
Roll the knit in a dry towel to press out water, reshape it, and lay it flat away from heat and sun. Do not wring, hang wet, or use a dryer.

What to avoid

Warm or hot water, steam, and the dryer — heat sets blood and felts wool.
Enzyme (biological) detergents and chlorine bleach; both attack wool protein.
The cotton method of pouring 3% hydrogen peroxide first. Peroxide can bleach and weaken wool. If a faint mark remains after soap, take the piece to a cleaner rather than oxidizing it at home.

Products

What to use

Related guides

FAQ

Questions people ask

Can I pour 3% hydrogen peroxide on wool the way I do on cotton?: No. Peroxide can bleach wool dye and weaken keratin. Stay with cold salt water and mild dish soap. If a shadow remains, take the knit to a cleaner instead of oxidizing it at home.
How do I lift dried blood that has already stiffened on a wool sweater?: Rehydrate the crust with repeated cold salt-water dabs for 20 to 30 minutes before adding dish soap. Do not soak and agitate a whole knit unless the label allows a still, cool hand wash.

Sources

Stain Removal Guide for Fabrics and Clothing — American Cleaning Institute