Anionic Surfactants in Cleansers and Foaming Products

Laundry products used to be harsh and hard on fabrics. Today’s cleansers are gentler and more effective, and much of the credit goes to a group of ingredients called anionic surfactants. You will find them in laundry detergent, dish soap, shampoo, and body wash.

Anionic surfactants are cleaning ingredients with a negatively charged head that attaches to water and a tail that grabs oil and dirt. They lift grime off fabric, hold it in the wash water, and create foam. Because they clean well on many soils, they are the most widely used surfactants in detergents and foaming cleansers.

Read on to see how they work, which ones you are likely to meet on a label, and the pros and cons of foamy products.

What Are Surfactants?

Surfactant is short for surface-active agent. It is the main cleaning ingredient in laundry detergent. Surfactants reduce the surface tension of the liquid they are added to, which helps water spread, wet fabric, and mix with oil.

Every surfactant molecule has two ends. The head is hydrophilic, so it is attracted to water. The tail is hydrophobic (also called lipophilic), so it is attracted to oil and grease. This two-part structure is what lets surfactants pull oily dirt away from fabric and keep it suspended in water.

The balance between the head and the tail also affects foam. Surfactants with a good balance tend to make stable foam, while those with a much stronger oily tail can work as defoamers.

Surfactants fall into four groups: nonionic, anionic, cationic, and amphoteric. They are classified by the electric charge on the hydrophilic head, which can be neutral, negative, positive, or either, depending on conditions.

Anionic Surfactants

Anionic surfactants are very common in laundry detergents and foaming cleansers. Their heads carry a negative charge. That charge helps them stay dissolved in water and keeps loosened dirt particles from clumping and settling back on your clothes.

They work on a broad range of soils and are especially good at removing oil and grease. That versatility is a big reason they appear in so many cleaning products.

How Do Anionic Surfactants Work?

When an anionic surfactant dissolves in water, its head carries a negative charge. The oil-loving tails stick to oily dirt and fabric, while the water-loving heads face the water. The tails surround the oily soil, and the negative heads point outward.

Since the surfaces of the dirt and the fabric both pick up a negative charge, they repel each other. This helps the dirt come off the fabric and stay in the wash water until it is rinsed away.

Anionic surfactants also produce more foam than most other types. Most foaming cleaners, including shampoos and body washes, are built on them.

Common Anionic Surfactants

Not every surfactant works equally well in a cleaning product, but anionic surfactants are the workhorses of the group. They include several families of compounds, such as alkylbenzene sulfonates, alkyl sulfates, sulfonic acid salts, and phosphoric acid esters.

Alkyl sarcosinates are another anionic type. They are used in detergents, personal care products, and many dishwashing and cleaning products.

Formulated Cleaners

Most household cleaners are formulated products. They are designed to clean different kinds of soil, so they combine several ingredients. The main ones are builders, hydrotropes, surfactants, and carriers.

Commodity Cleaners

Commodity cleaners are the opposite. They target one kind of soil and often consist of a single chemical.

In formulated cleaners, the surfactant type depends on the dirt you want to remove. For laundry, anionic surfactants usually work best. Hydrotropes keep the surfactants and builders evenly mixed and stable, and the carrier is either water or a solvent.

Anionic Surfactants in Laundry Detergent

Surfactants make cleaning products work better by reducing surface tension, which helps carry dirt away. Of all the types, anionic surfactants are the most common in laundry detergent. They can also irritate skin in some people, depending on the type and how well they are rinsed out.

You will find them in nearly every kind of cleaner, from laundry detergents and dishwashing liquids to skincare products. The anionic surfactants in laundry detergents are often made from fatty alcohols, which can come from plant or petroleum sources.

The type of surfactant affects whether a product feels harsh or mild. Sodium lauryl sulfate (SLS) is a common anionic surfactant in cleansers and some detergents. It cleans and foams well but is more likely to irritate skin.

A closely related compound, sodium laureth sulfate (SLES), is used in many products in its place. It is generally less irritating and gives a milder cleanser. Potassium cocoate, made from oils and fats, is another milder anionic surfactant you may see in soap-based products.

Beyond surfactants, a typical powder or liquid laundry detergent includes several other parts:

• Surfactants: The main cleaning ingredient. They remove dirt and soil.
• Builders: These soften hard water by tying up minerals. Common builders include sodium carbonate, sodium silicate, and zeolites. Phosphate builders such as sodium tripolyphosphate have been banned or limited in many places.
• Fillers: Used mostly in powders, they help the product pour and dissolve evenly and keep it from clumping into a hard block.
• Bleaching agents: These help remove stains and brighten whites. Most detergents use oxygen-based bleach rather than chlorine bleach.
• Enzymes: These break down protein, starch, and fat stains so the surfactants can rinse them away.

Other nonessential ingredients include fragrances, dyes, preservatives, and foam regulators.

Read More: What Makes Laundry Detergent Eco-Friendly?

Anionic Surfactants in Foaming Products

More foam does not mean cleaner laundry. In fact, too much foam can get in the way in a washing machine, and high-efficiency (HE) machines are designed for low-suds detergents. Foam is more useful in products like car wash soap, shampoo, and body wash, where it helps loosen dirt and shows you where you have applied the product.

The charge on an anionic surfactant’s head helps it form stable foam. That is why foaming products are usually built on anionic surfactants.

Cationic and nonionic surfactants foam less. They are common in fabric softeners and in low-foam cleaners.

SLS and SLES are the surfactants most often used to make foam. Both are alkyl sulfates made from fatty alcohols, and their structures are very similar, so one can often replace the other. Because SLS is more likely to irritate skin, many makers prefer SLES.

Both ingredients are widely used in cleaning and personal care products, and irritation is the main concern with them. They are not classified as carcinogens.

Formulators often get the best foam by blending a primary surfactant such as SLES with a secondary one such as an alkanolamide.

It is a myth that every foamy cleanser irritates skin. If you know the irritating ingredient is the problem, you can simply pick a foaming product without SLS.

Read More: Can Your Detergent Impact Your Acne and Skin?

Conclusion

Surfactants can irritate skin and, at high concentrations, harm aquatic life. Used in the right amounts and in well-chosen formulas, they are what make modern detergents work.

Anionic surfactants are the most popular choice in cleaning products, from detergents to personal care items, because their negative charge helps them lift dirt, stay dissolved, and foam.

If your skin is sensitive, check the label and look for milder surfactants, such as SLES in place of SLS, plus fragrance-free and dye-free formulas. Measure your detergent carefully and rinse well. And if a detergent still bothers your skin, talk with a dermatologist rather than guessing.