How Laundry Detergent Works

By: Emily Frydendall  | 
Since the 1940s, laundry detergents have been a necessity in most households for cleaning fabrics.
© sb-borg

Key Takeaways

  • Laundry detergents clean fabrics. Surfactants are the key ingredient that allows detergents to remove dirt and stains by interacting with both oil and water.
  • Modern detergents contain a mixture of surfactants, enzymes and other ingredients to tackle various stains and fabric care needs.
  • The choice between powder and liquid detergents often comes down to personal preference, although environmental considerations and packaging waste are increasingly important factors for consumers.

Nothing beats the feeling of putting on a clean T-shirt, especially after a shower. It leaves you feeling fresh and ready to take on the day. And where do these clean T-shirts come from? Ah, yes -- the laundry, that household chore that never seems to go off of your to-do list. Even the numbers agree: The average American family does about 300 loads of laundry per year [source: Wall Street Journal].

You may find yourself constantly putting clothes and sheets in the wash because, put simply, people are dirty. We sweat, shed skin cells and come into contact with food, dirt and many more particles every day. Consequently, we need a way to effectively get clothes and fabrics clean to maintain personal hygiene and keep up the appearance of garments. But what exactly is going on in that washing machine to get our clothes and fabrics clean? The secret is laundry detergent.


Prior to the invention of laundry detergents, Americans used soap flakes to wash clothes. However, in the 1930s, the first laundry detergent, Dreft by Procter & Gamble, hit the market. Later, in 1943, Procter & Gamble produced Tide, which could get out tougher stains due to the use of some very unique chemical ingredients. Since the 1930s and 1940s, laundry detergent has become a household necessity that is used around the world to clean fabrics. So how exactly do laundry detergents get your clothes clean? In this article we are going to get to the bottom of what happens when detergents enter your washing machine.

First up: laundry detergent ingredients.


Surfactants: Laundry Detergent's Cleaning Power

All laundry detergent ingredients have a job to do, but the one group that's really crucial to getting your clothes clean are surfactants. The word surfactant stems from the combination of words "surface-active agents." Surface-active agents get their name from their unique chemical structure, which allows them to interact with two different types of surfaces, such as oil and water. The tail of a surfactant molecule is hydrophobic, or not attracted to water. What the hydrophobic end is attracted to is grease and dirt. The head of the surfactant molecule, on the other hand, is hydrophilic -- it's attracted to water [source: Silberberg].

So when a greasy piece of clothing is immersed in water with detergents containing surfactant, the tail of the surfactant molecules attach to the grease, and the head end of the molecule is attracted to the water. When the washing machine agitates the clothes, the molecules form tiny spheres, which stay suspended in the water and are rinsed away when the water is drained. Therefore, the prime benefit of surfactants is their ability to draw grime out of clothing while making sure it doesn't return to the fabrics.


Essentially, there are four main types of surfactants, with the first three used the most in laundry detergents, and their actions depend on their interactions with ions. Ions are charged particles due to the gain or loss of electrons. Ions can be positive such as calcium, Ca2+, or negative such as chloride, Cl-.

  1. Anionic surfactants are negatively charged in solution. However, they do not work as well by themselves in hard water. This is because hard water has many positively charged ions presents such as calcium (Ca2+) and magnesium (Mg2+). Since anionic surfactants are negative they are attracted to the positive ions and bind, making them unable to bind to other molecules in solution.
  2. Nonionic surfactants have no charge. Therefore, they are not as easily impaired under hard water conditions, since they are not attracted to the positive ions.
  3. Cationic surfactants are positively charged in solution. They help the anionic surfactant molecules pack in at the water/dirt interface thereby allowing the anionic surfactants to pull more dirt away.
  4. Amphoteric or zwitterionic surfactants are both positively and negatively charged. These surfactants are very mild and are often found in gentler cleansers such as hand soaps, shampoos and cosmetics. [source: Silberberg].

Read on to learn about some other ingredients that help detergents do their job.


Additional Components of Laundry Detergent

Although surfactants are at the heart of laundry detergent's ability to clean fabrics, other ingredients can help detergents clean better, brighten clothes or smell better. As described previously, some types of surfactants typically do not work well in hard water due to the excess positive ions present. Additives called builders can help detergents to work better under hard water conditions. Builders accomplish this feat by removing calcium (Ca2+) and magnesium (Mg2+) ions in hard water by binding to them. This allows the surfactants, especially anionic surfactants, to bind to more grime, rather than the positively charged ions in the wash water. Builders also are bases, so they work to neutralize acid and can help disrupt chemical bonds. Another benefit of adding builders to laundry detergents is that manufacturers can use less surfactant, since the builders make the surfactant more efficient. Some examples of builders include sodium tripolyphosphate (STTP) and zeolites [source: EPA].

Detergents can also include components that make clothes whiter or brighter. The most common whitening agents are bleaches. Bleaches contain peroxides, which can oxidize fabrics [source: EPA]. Fluorescent whiteners and brighteners are also added to some laundry detergents because they minimize the yellowing of fabrics. These additives work by absorbing ultraviolet light and emitting back visible blue light, which can mask the yellow that may make colors appear faded and whites appear dingy.


Enzymes are naturally occurring biologic agents present in many detergents in varying concentrations. These enzymes are typically classified into the following categories and are similar to the enzymes used by your body to digest food:

  • Proteases: help break down proteins
  • Lipases: help break down fat
  • Amylases: help break down starches [source: Basketter]

These enzymes help break down food particles that are present on clothing by catalyzing, or speeding up, the decomposition process. A point to consider is that enzymes are biological products that can break down over time. Therefore, detergents can also contain enzyme stabilizers, which protect the enzymes and help them function.

Some other components include fragrance and coloring, which give laundry detergents their distinctive scents and appearance. Detergents sometimes contain trace amounts of dye, which is not enough to dye your actual clothing. However, on top of making your laundry detergent more visually appealing, dyes can show you when there is still detergent left on your clothes after the wash cycle.

Lastly, fillers help dilute and distribute the active ingredients to their proper dosages. Powder and liquid detergents use different fillers. The major filler in powder detergents is sodium sulphate, which provides the granular powdery texture. The primary filler in liquid detergents is water.

In the next page, we will examine some more similarities and differences between powder and liquid detergents.


Powder vs. Liquid Detergents

Laundry detergent manufacturers have come a long way since the first box of Tide was produced more than 60 years ago. Currently, the two main types of laundry detergent are powders and liquids. For the most part, powder and liquid detergents share the same active ingredients except for the filler used. Additionally, powder and liquid detergents both have pros and cons, and since they have similar cleaning power, people usually choose which type to use based on personal preference.

Here are some of the advantages and disadvantages of using powdered detergents:


  • Pro: They're generally cheaper.
  • Pro: The cardboard packaging is more eco-friendly.
  • Con: Some people think they don't dissolve as well in water. This may have been a problem with some of the first powdered detergents, but these days, most powders are designed to readily dissolve in water.
  • Con: Sodium sulphate can wreak havoc on septic systems.
  • Con: Powders contain more chemicals compared with liquids, due to the filler.

People may or may not use liquid detergents for an entirely different set of reasons:

  • Pro: The detergent is already pre-dissolved.
  • Pro: You can pre-treat stains by pouring it directly onto clothes.
  • Con: They're usually more expensive than powdered detergent.
  • Con: They have plastic packaging, which is less eco-friendly.


Environmental Considerations with Laundry Detergent

Even though detergents do a tremendous job of getting rid of the dirt and grime in our fabrics, at what cost does this come? Considering the toxicities of their chemical ingredients and carbon cost of production, it's not surprising that some people have concerns about the impacts of laundry detergents on the environment.

Their carbon footprint alone is significant by many people's standards. Carbon footprints are an indicator of the amount of carbon dioxide (CO2) produced while making, shipping and using a product. According to the Wall Street Journal, the carbon footprint of using UK detergent brand Tesco, varies from 1.3 pounds (0.6 kilograms) to 1.9 pounds (0.9 kilograms) per load, depending on the form of the detergent that's used. To put this in perspective, it is estimated that for every mile an average car travels, 1 pound (0.5 kilograms) of CO2 is emitted. Recall that American families on average do 300 loads of laundry per year. This means that the carbon footprint of laundry detergents for one year of laundry is approximately 480 pounds (218 kilograms) per year, or about 10 pounds (4.5 kilograms) per week. So, while this may not seem like a lot, especially if your car produces about 5 tons of CO2 per year, this number only reflects the laundry detergent. It does not factor in the extra energy requirements of running the washer and dryer [source: Wall Street Journal].


Now, add to that the toxic effects of the chemical components in detergents. According to the EPA, some of the major concerns about the chemical ingredients used in laundry detergents include the following:

  • Toxicity to aquatic organisms and algae
  • Persistence in the environment
  • Eutrophication of fresh water, particularly by phosphate-based detergents (now, phosphates have been replaced by zeolites which may be alleviating this problem)
  • Health problems in people, such as cancer [source: EPA]

Another concern relating to laundry detergent is that it can make the wash water acidic, and depending on where that water runs to, it could further impact the environment, having effects similar to acid rain. Read on to the next page to find some green alternatives to regular detergents.


Green Laundry Detergent Options

Given some of these environmental considerations about laundry detergents, there are some greener options available to today's consumer. Most detergents marketed as environmentally friendly don't include perfumes or dyes, and they're typically phosphate free, biodegradable, and they haven't been tested on animals.

One eco-conscious option is detergent designed to work well in cold water. On average, 80 to 85 percent of the total energy used washing a load of clothes goes to heating up the water [source: Sabaliunas et al.]. Washing in cold water saves energy, which can translate to savings on your household energy bills, too.


Another environmental approach is to use concentrated formulas, which cuts down on packaging and on the amount of water it takes to make the detergent. According to Proctor & Gamble spokeswoman Carol Berning, concentrated detergents require "less plastic for bottles, less corrugated cardboard for crating, and less gasoline used, because we need less trucks to move the shipments" [source: Consumer Reports]. The cold water and concentrated options that different companies manufacture may be one step to greener washing practices. However, even in these forms, the detergents still contain some potentially environmentally hazardous chemicals.

An additional green choice -- for the benefit of the environment and you wallet -- could be making your own laundry detergents. There are a variety of recipes out there, with the common ingredients of water, bar soap, borax and washing soda. Some environmental benefits of making your own laundry detergent are that they typically use fewer chemicals and additives, and they can save on packaging. However, be aware that clothing washed with homemade detergent may also require bleaching, and it may not get stains out as well as some of the commercially produced detergents.

Clearly, detergents are chemically complex products that are continually being improved upon, whether it is boosting their stain-fighting powers or making them greener. For lots more information on laundry detergents and related topics, follow the links below.


Frequently Asked Questions

How does hard water affect laundry detergent efficiency?
Hard water contains minerals that can interfere with the action of detergents, reducing their cleaning power. Some detergents include water softeners to counteract this effect.
Are eco-friendly laundry detergents as effective as traditional ones?
Eco-friendly detergents can be just as effective as traditional detergents. They use diifferent ingredients or formulas to achieve similar results without harmful chemicals.

Lots More Information

Related HowStuffWorks Articles

More Great Links

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