Fels-Naptha is a brand of bar laundry soap used for pre-treating stains on clothing and as a home remedy for exposure to poison ivy and other skin irritants. Fels-Naptha is manufactured by and is a trademark of the Dial Corporation.
The soap comes packaged in paper similar to bar body soap and is most often found in the laundry section of a supermarket or grocery store. It is used in the pre-treatment of stains by rubbing the dampened product on a soiled area prior to laundering, and is claimed by the manufacturer to be most effective in removing chocolate, baby formula, perspiration, and make-up.[1]
The original Fels-Naptha, developed by Philadelphia manufacturer Joseph Fels around 1893, was used as a home remedy in the treatment of contact dermatitis caused by exposure to poison ivy, poison oak, and other oil-transmitted organic skin-irritants. Washing the skin directly with the soap helps break up the oils that carry the toxin. However, in its own caution use sheet, Dial Corp. stated that Fels-Naptha is a skin irritant and not to be used directly on skin.[2] Grated and added to a wash cycle, about 1/16th a bar's worth of Fels-Naptha per load, is said to eliminate residual resins that can remain in clothes up to a year, according to the manufacturer.[1]
Fels-Naptha used to contain Stoddard solvent, a skin and eye irritant. According to the ingredients list on the Fels-Naptha website, Stoddard solvent is no longer included in the soap.[1]
According to the "Chronic Health Effects" section of the National Institutes of Health's MSDS for the original formulation of Fels-Naptha:
Chronic toxicity testing has not been conducted on this product. However, the following effects have been reported on one of the product's components. Stoddard solvent: Repeated or prolonged exposure to high concentrations has resulted in upper respiratory tract irritation, central and peripheral nervous system effects, and possibly hematopoetic, liver and kidney effects.
Stoddard solvent is another name for mineral spirits, which are, like petroleum distillates, a mixture of multiple chemicals made from petroleum. Exposure to Stoddard solvent in the air can affect your nervous system and cause dizziness, headaches, or a prolonged reaction time. It can also cause eye, skin, or throat irritation.[3]