Fels-Naptha is a laundry bar soap that people reach for when a stain needs pretreating. Most of the questions about it come down to one thing, which is how to use the bar well. The maker gives a short method for stains and a separate method for boosting the wash. Both are simple, but the details matter for fabric care, colors and skin contact.
Start by checking the care label and patch test an inconspicuous area. Wet the stain, rub the bar onto it, and wait one minute before washing as normal. Keep the bar away from eyes and skin, and out of reach of children.
What it is
Fels-Naptha is a laundry bar soap that the maker sells as a stain pretreater and laundry booster. The maker's ingredient page lists beef tallow, palm oil, palm kernel oil and sodium hydroxide among its components. The bar is meant to be rubbed onto stains before washing or grated into the wash.
According to the maker
What to use it on
Stain pretreating
Fels-Naptha is aimed at grease, oil, dirt, sweat, blood, wine, grass, sauces, baby food and beverages. Wet the stained spot first, then rub the bar directly onto it.
Wait one minute before washing the item as normal. Check the care label before you start, since the maker says to patch test first.
Collars and cuffs
The maker lists collars and cuffs as a place to use the bar, and ring-around-the-collar is one of the stains it targets. Wet the soiled area, rub the bar into it, and wait a minute before washing. Patch test an inconspicuous area first, as the maker advises, and check the care label.
Gym gear and uniforms
The maker lists gym gear, uniforms and cloth diapers among the fabrics it suits. Grass and dirt are among the stains it targets, so grass-stained baseball pants are a direct match for the stain method.
Wet the stain, rub the bar onto it, wait one minute, and then wash as normal. Check the care label on the pants first, since the maker says to do that before any use.
Whites and soaking
The maker lists whites as a use, with a soak. Wet the item, work the bar into the stained area, and let it soak before washing. The maker's directions give no soak time, so use the care label as your limit and do not leave the item soaking longer than the fabric allows.
Shoes and fabric furniture
The maker lists shoes, fabric furniture and garbage bins as uses. Fabric furniture needs the bar diluted, though the maker gives no ratio, so test a hidden spot first. The maker gives no separate directions for shoes or bins, so check the item's material before you try it.
5 steps
How to use it
- 1
Check the care label first
The maker says to check the garment care label and patch test an inconspicuous area before use. The maker lists no specific fabrics to avoid, so the care label is the main limit. Do this before you treat any stain.
- 2
Wet the stain
Start by wetting the stained spot. The maker's directions put this step first, before any bar is applied.
- 3
Rub the bar onto the stain
Rub the bar directly onto the wet stain. Then wait one minute before you move on to washing.
- 4
Wash as normal
After the minute, wash the item the way you usually would. The maker's directions do not give water temperature or cycle settings.
- 5
Use the bar as a booster
For a booster, grate 1/16 of the bar into the washer along with your detergent. The maker presents this as a separate method from stain treatment.
Where not to use it
The maker lists no specific surfaces it says to avoid. It does say to check the garment care label and patch test an inconspicuous area before use. If a care label rules out a fabric, follow the label and skip the bar for that item.
Safety
The maker's October 2025 safety sheet doesn't classify the bar as hazardous under OSHA rules and gives no warning word, but it says to avoid contact with eyes and skin. Prolonged contact may cause temporary eye irritation and dry skin, so keep it out of reach of children. The maker gives no mixing warnings, so don't combine it with other cleaners unless the label allows it.
Never mix chlorine bleach with vinegar or other acids, ammonia or rubbing alcohol. Poison Control: 1-800-222-1222.
Versions the maker sells
Where to buy
Fels-Naptha Laundry & Stain Remover Bar
Sponsored links: as an Amazon Associate we earn from qualifying purchases. Product facts come from the maker's own instructions and labels.
Questions
Does Fels-Naptha have good reviews?
No customer opinions are in the maker's information, so none are quoted. What the maker does say is that the bar is for grease, dirt and sweat stains on most fabrics, with collars, cuffs and whites among its uses. Its stated limits are the care label, a patch test, and keeping it away from eyes, skin and children.
Does Fels-Naptha work on old stains?
The maker's directions do not address old or set-in stains, so no promise is made for them. The method it gives is to wet the stain, rub the bar on it, and wait one minute before washing. Test a hidden area first before repeating the method.
Can Fels-Naptha be used on poison ivy?
Poison ivy is not among the stains the maker lists, so its directions do not cover it. The bar is labeled for stains such as grass, grease, dirt and sweat, not skin reactions. For a skin reaction, follow advice from a doctor or pharmacist rather than laundry directions.
How much Fels-Naptha do you add as a booster?
The maker says to grate 1/16 of the bar into the washer with detergent. That is a small amount, so grate a little rather than the whole bar. The bar is used with your detergent, not in place of it.
How does Fels-Naptha compare with Zout?
Zout is a triple-enzyme spray for pretreating, while Fels-Naptha is a bar. Zout's maker says it suits most colorfast washable fabrics, including delicates, and targets protein, starch and oil stains such as blood, grass and sweat.
Fels-Naptha's maker lists most fabrics too, and targets grease, dirt, sweat, blood and grass. Neither set of facts shows one as better, so choose by the stain and the fabric.
What is in Fels-Naptha?
The maker's ingredient page lists beef tallow, palm oil, palm kernel oil, sodium hydroxide and sodium chloride, among others. The October 2025 safety sheet names only glycerin, at 7 to 10 percent, and the maker's ingredients differ, so check the package label. The two lists differ, so check the package label for the current list.
How does Fels-Naptha compare with other bar soaps?
The maker's facts here cover only Fels-Naptha and Zout, so no other bar soap is compared. Other products are not described in these facts, so the facts give no ingredients or directions for them. Read each product's own label before choosing one.
Where it shows up in our guides
More product guides
How we know this
Every use, amount and warning here comes from the maker's product pages, labels and safety data sheets.