The Stain Library

How to remove baby sick from a plastic food container

  • DifficultyEasy
  • OutlookUsually removable
  • MaterialPlastic food container
  • Reviewed7 September 2026

The short answer

Take the lid apart before washing anything. Almost every food container has a removable silicone seal, and the groove it sits in holds liquid that never dries out. Wash the box, the lid and the seal separately in warm soapy water, dry everything, and only then reassemble. If the container still smells, a bicarbonate of soda paste left in it for an hour will deal with it.

If it has just happened

Rinse it out with warm water and pull the lid seal out. Doing that now, rather than after a dishwasher cycle, is what stops the smell.

Heat can set this stain permanently

Do not use hot water, a tumble dryer, an iron or a steam cleaner until the mark has gone. Heat fixes this type of stain into the fibres and makes it far harder to shift.

Cleaning the mark is not the same as disinfecting

If the sickness came with a stomach bug rather than an ordinary posset, the surface may carry norovirus, which spreads easily and survives on hard surfaces. UK public health guidance is to wear gloves, avoid shaking contaminated laundry, wash affected laundry separately with normal powder at 60 C where the care label allows it, and disinfect compatible hard surfaces with a bleach based product afterwards. Do that after the stain work, not instead of it, and only where the material tolerates it.

Keep every kind of drying heat away until the mark has gone

Baby sick is mostly milk protein. Heat coagulates protein and locks it into the material, which is why a mark that would have washed out can become permanent after one hot wash, one pass with an iron, a hairdryer or a spell on a radiator. Cool or warm treatment, air drying, and a proper look in daylight before anything warm goes near it.

What you will need

  • Disposable gloves Sickness that came with a stomach bug is a hygiene job as well as a stain.
  • A plastic scraper or spatula Plastic, not metal. A scratched plastic surface holds dirt in the scratches for good.
  • Kitchen roll For lifting the bulk before any water is involved.
  • Warm soapy water Warm rather than hot, and washing up liquid rather than anything stronger.
  • A soft cloth or a soft nylon brush Soft. Nothing green, nothing wire and nothing gritty.

Helpful but not essential

  • Bicarbonate of soda A mild paste for a textured surface or a lingering smell.

Fresh baby sick on plastic food container

Nothing absorbs, so this is washing rather than stain removal.

  1. Lift the solids off with a plastic scraper

    Plastic rather than metal, so the surface is not scored. Straight into a bag rather than wiped along the surface.

  2. Wash with warm soapy water

    Warm rather than hot, because heat sets milk protein and can distort a plastic. Washing up liquid and a soft cloth is the whole product list.

  3. Work any texture or seam with a soft brush

    Moulded plastics have corners, ribs and seams where a cloth passes over. A soft nylon brush reaches them without scratching.

  4. Rinse and dry

    Rinse every part under warm running water and dry them separately before reassembling, because a container put back together damp is a container that smells.

  • How longFive minutes
  • RepeatingOne wash is normally enough.
  • Stop ifthe surface is clean, rinsed and dried

Dried baby sick on plastic food container

Soak it. Dried milk on a non porous surface softens off completely given a little time.

  1. Soak rather than scrape

    Warm soapy water left on the mark for ten or twenty minutes lifts dried milk off a plastic surface. Scraping at it is how these surfaces get scratched.

  2. Wipe it away with a soft cloth

    If it is not moving, leave the water on it longer. There is no stain in the material, so time always works eventually.

  3. Use a bicarbonate paste on a textured area

    A little bicarbonate of soda mixed to a paste is mildly abrasive at worst and mildly alkaline, which suits milk residue and does not scratch.

  4. Rinse thoroughly and dry

    Rinse every part under warm running water and dry them separately before reassembling, because a container put back together damp is a container that smells.

  • How longTwenty minutes
  • RepeatingSoak again rather than scrubbing harder.
  • Stop ifthe residue has softened and washed off without any scratching

Old or set in baby sick on plastic food container

An old mark on plastic is usually a smell or a stain in the surface texture.

  1. Give it a long soak in warm soapy water

    Several hours or overnight. On plastic, contact time does everything that scrubbing would and none of the damage.

  2. Then an oxygen soak if the item allows it

    An oxygen based product in warm water lifts the yellowing that milk fat leaves on plastic. It is far gentler than chlorine bleach and it does not attack the material.

  3. Deal with the smell separately

    Bicarbonate of soda paste left on the surface for an hour, then rinsed, takes out a sour smell that washing has not.

  4. Then weigh it against replacing the item

    Most things in this family are inexpensive and are meant to be replaced when they are worn. A scratched, stained or smelling plastic item is usually at the end of its life rather than in need of another treatment.

  • How longOvernight
  • RepeatingOne long soak, then accept it or replace the item.
  • Stop ifthe surface is clean and free of smell, or the item is worn enough to replace

What not to use on plastic food container

  • Abrasive pads, scouring powder and wire wool

    Plastics are soft and scratch easily, and a scratched surface holds residue in the scratches and looks progressively worse. On a food surface, scoring also gives bacteria somewhere to live.

  • Solvents, white spirit and nail varnish remover

    Many plastics are attacked directly by solvents, which produces a permanently dull, sticky or crazed patch. There is nothing a solvent achieves on a milk mark that warm soapy water does not.

  • Very hot water and dishwasher cycles before the mark has gone

    Milk protein sets with heat, and heat also distorts or crazes many plastics. Deal with the mark warm, and use the dishwasher afterwards if the item is dishwasher safe.

  • Putting it straight in the dishwasher with the residue still in it

    A dishwasher cycle is hot enough to set milk protein into the surface texture and into the lid seal. Rinse it out first, then use the dishwasher.

White compared with coloured plastic food container

Clear and white polypropylene yellows over time where milk fat has oxidised on the surface, and that is what makes an old baby bottle or food box look tired. An oxygen based soak lifts it. Chlorine bleach is the wrong tool: it yellows polypropylene over repeated use rather than whitening it, and on anything that holds food it is not worth the risk of residue.

If the mark is still there

If it still smells after washing, work through the parts rather than washing the box again. The seal, the groove it came out of, the lid threads and any vent flap are the four places that hold residue.

A bicarbonate of soda paste smeared inside the box and left for an hour, then rinsed, is the standard answer for a smell and it works better than repeated washing.

For a yellow tinge, an oxygen based soak in warm water for a few hours lifts most of it. If the plastic is also slightly tacky to the touch, that is degradation rather than residue and the container has reached the end of its life. Replacement seals are sold for most branded containers.

When to stop and call someone

Replace the container, or at least the lid seal, rather than persisting if a smell survives a full strip down and an overnight soak, or if the plastic has yellowed and gone slightly tacky. Replacement seals are sold for most branded containers and cost very little.

Why baby sick behaves this way on plastic food container

A plastic food container is a moulded box, a lid and usually a silicone gasket.

The box is the easy part

Non porous, dishwasher safe in most cases, and cleaned by detergent.

The seal is where it hides

The gasket pulls out of a groove in the lid, and that groove holds liquid indefinitely because it never sees air. A container that smells of sour milk after a dishwasher cycle almost always has residue there.

Milk fat yellows plastic

Oxidised milk fat leaves a yellow cast, particularly on clear and white polypropylene. Oxygen products lift it; chlorine bleach makes it worse.

Heat before cleaning is the trap

A dishwasher cycle bakes milk residue into the surface texture, which is why the order matters here as everywhere else.

Sources

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

  1. Melamine dinnerware and staining, G.E.T. manufacturer

    Melamine manufacturer guidance that staining is caused by food left to dry on the surface and by protein and hard water minerals building up, that an oxygen releasing soak or an overnight soak in warm water with dishwashing granules removes the stains, that a non abrasive pad is used afterwards, and that bleach, green scouring pads, steel wool and metal scourers must not be used because they dull and scratch the surface.

    Checked 7 September 2026

  2. Bathroom care guide, Carryduff Designs manufacturer

    UK bathroom supplier guidance that acrylic is softer than china and scratches, that scouring products are not recommended, that chemicals including nail varnish remover, household bleach, perfume and strong disinfectant must never be used on acrylic, that warm soapy water or a mild cream cleaner is the correct clean, that mild limescale removers are acceptable occasionally, that bleach must not go in a cistern, and that cleaners must never be mixed because they give off poisonous gas.

    Checked 7 September 2026

  3. How to remove baby formula stains, Purex Stain Lab manufacturer

    Manufacturer guidance identifying breast milk, formula and baby spit-up as protein stains, explaining the role of enzymes, and warning that the mark should be checked before any drying heat because heat sets what remains.

    Checked 7 September 2026

  4. Norovirus: what to do and how to stop the spread, UK Health Security Agency authority

    UK public health guidance establishing that illness related vomit can carry norovirus, that contaminated laundry should be washed with normal powder at 60 C where the care label permits, and that compatible hard surfaces should be disinfected with a bleach based product.

    Checked 7 September 2026