Material
Baseball cap
Cotton or polycotton with a stiffened brim that may be cardboard. The fabric washes easily and the brim decides whether the cap can be wetted at all.
- SurfacePorous
- WashingMachine
- Colour run riskMedium
- Reviewed7 September 2026
What baseball cap can and cannot take
- Heat Use with care
- Water and soaking Tolerates it
- Acids, including vinegar Tolerates it
- Strong alkalis Tolerates it
- Solvents Use with care
- Chlorine bleach Use with care
- Abrasives Use with care
Always test on a hidden area first and let it dry before you treat the visible mark.
General rules for baseball cap
Spot clean by hand and keep the brim dry wherever you can. That is the safe default whatever the cap is made of.
If the brim is plastic, which you can usually tell because it flexes back cleanly and does not feel papery, hand washing the whole cap in cool water is fine.
Never put a cap in a washing machine or a dishwasher. Both soak the brim and the second one adds heat, which is the worst possible combination for a stain that sets with heat.
Check the label
The peak is the problem. Older and cheaper caps have a cardboard stiffener inside the brim that softens, warps and can bleed brown when it gets wet. Newer ones use plastic and are safe to wash. Feel the brim and flex it before deciding.
Stains on baseball cap
- Baby sick Flex the peak before doing anything. If it feels papery and creases rather than springing back, the stiffener...
- Blood Blot first, then use cold water and a tiny amount of compatible detergent. Work from the edge, rinse or blot...
- Body oil Blot baseball cap, pretreat a permitted washable patch with liquid detergent, rinse and use a cool labelled w...
- Breast milk Blot and cold-rinse a label-approved washable item. Use your compatible biological liquid detergent and a per...
- Bronzer Lift loose bronzer from baseball cap before it is rubbed in. Blot cream bronzer, follow the material or care...
- Coffee Blot first. If the label permits, gently rinse cool water through the back of the mark, supporting the fabric...
- Concealer Lift the concealer, flush Baseball Cap from the back with cool water, pre-treat the oily residue with one dro...
- Cooking grease Lift and blot cooking grease from Baseball Cap, absorb the oil, pretreat both sides with washing-up liquid fo...
- Deodorant Rub a fresh white deodorant mark off baseball cap while it is dry. For residue that remains, follow the care...
- Hair dye Blot hair dye from Baseball Cap, test the mildest compatible cool detergent route, clean inwards, remove resi...
- Lipstick Lift lipstick from Baseball Cap, work from the reverse with a drop of washing-up liquid, rinse cool, wash to...
- Motor oil Blot motor oil from Baseball Cap, absorb the residue, pretreat both sides with a little washing-up liquid, wa...
- Nail polish Lift accessible free polish without rubbing and keep the item dry. The fibre, finish or construction makes a...
- Period blood Lift any tissue with a spoon edge, then blot. Use cold water and a tiny amount of compatible detergent for th...
- Pet urine Blot until nearly dry, then use only the cool-water quantity baseball cap can tolerate. Use a labelled pet ur...
- Sweat Rinse fresh sweat from the back of Baseball Cap with cool water, pretreat retained residue, wash to the care...
- Tomato sauce Lift tomato sauce from Baseball Cap, flush from the reverse with cool water, pretreat the remaining film, was...
A cap is simple fabric wrapped around one problematic component.
The brim stiffener
Cheaper and older caps use a card or fibreboard insert. Soaked, it swells, warps and can leach a brown tannin stain out into the fabric of the peak. Once warped it does not flatten again. Plastic inserts, standard on most modern caps, have none of these problems.
The crown is ordinary fabric
Cotton or polycotton, which takes enzymes and a cool soak like anything else.
Shape is easily lost
A wet cap dried flat or squashed dries into that shape. Dry it over something round, a mixing bowl or a tin, so it keeps its form.
Sweat marks are a separate issue
The band inside a cap is often already stained, and treating the milk mark will not touch that.
Sources
What we checked and when. Where a manufacturer instruction disagrees with anything here, follow the manufacturer.
-
How to remove stains from baby clothes, Persil UK
manufacturer
UK manufacturer guidance to act quickly on formula, blot when immediate washing is impossible, rinse under cool water, soak for at least 15 minutes where the care label permits, pre-treat with detergent and then wash to the care label.
Checked 7 September 2026
-
A guide to newborn laundry, American Cleaning Institute
trade body
Cleaning trade body guide to pre-treat breast milk, formula or spit-up with an enzyme stain remover, soak fresh marks for at least 30 minutes and older marks for several hours, launder, and keep stained items out of the dryer until the mark has gone.
Checked 7 September 2026
-
How to clean polyester and synthetics, Woolite
manufacturer
Detergent manufacturer guidance that polyester is washed, dried and ironed at low to medium heat only because excessive heat can melt the fibres, that air drying is preferred to machine drying, that nylon is washed in cool water on a gentle cycle because repeated machine washing causes discolouration and loss of shape, and that acrylic knits are laid flat or dried at low temperature to keep their shape.
Checked 7 September 2026