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Most car shampoos contain unwanted chemicals

Car shampoo may contain substances that are allergenic and environmentally harmful. In general, it is worth considering the use of car shampoo that can contaminate the environment or groundwater.

Katja Laukkonen Ravn · Foto: Getty Images · 18. marts 2024
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Car shampoo may contain substances that are allergenic and environmentally harmful. In general, it is worth considering the use of car shampoo that can contaminate the environment or groundwater. 

It is difficult to find good choices of car shampoo or auto shampoo for car washing, that are free from problematic chemicals. 

A total of 19 out of 21 car shampoos in our test contain preservatives that are allergenic and may be problematic to the environment. or lack a full ingredient list. This means we don't know what's in them. 

These substances are common in car shampoos 

In most car shampoos, we have found the substances isothiazolinones, which are allergenic preservatives and may be problematic for the environment. 

For example, the highly allergenic substance methylisothiazolinone (MI), which is also found in paint. 

In recent years, there have been more and more cases of allergy to methylisothiazolinone. 

Once you have developed an allergy to MI, even small amounts of the substance can cause rash or itching on the face and hands. 

Several car shampoos lack ingredient lists 

For washing and cleaning agents, it is mandatory to disclose the full ingredient list on the company's website. But there are problems with this – 20 of 21 car shampoos did not comply.

Several car shampoos also received the worst rating in the test, the C-rating, because we cannot obtain information about all the ingredients. 

"We have repeatedly tried to contact the companies and requested the full ingredient list, but without success. Therefore, we cannot recommend the product when we actually do not know what is in it," says test manager Christel Søgaard Kirkeby. 

Some car shampoos also lack hazard labeling, ingredient lists, and safety instructions in Danish.  

A single car shampoo is without unwanted chemicals 

The only goodchoice in the test is a car shampoo from Biltema. However, you should be aware that Biltema sells several different car shampoos. Two other car shampoos from Biltema are included in the test, which receive the lowest rating, the C-rating. 

Even if a car shampoo gets an A-rating in the test, you should generally consider the use of car shampoo that can pollute the aquatic environment when using it. Regardless of which chemicals are in it. 

The Nordic Swan-labeled car wash is better for the environment 

Car shampoo for home washing can be easy and cheap, but it is more environmentally friendly to have your car washed in a car wash -  preferably a Nordic Swan-labeled car wash. 

Car shampoo and the dirt from your car, which can contain heavy metals, oil residues, or brake dust, end up in the wash water and thus in the environment. When you wash your car yourself, you risk all of this ending up in the water environment or groundwater. 

Therefore, danish authorities recommend washing the car in a Nordic Swan-labeled car wash instead of washing the car with car shampoo in the driveway. 

In a Nordic Swan-labeled car wash, the water is cleaned and recycled. This can save both on water consumption and pollution of the environment.  

Check where the wastewater ends up 

If you wash the car in an area where the wash water can seep down, such as a gravel area, the substances can penetrate the soil and move towards groundwater or a nearby stream. 

If you wash your car in a location where the water is led to the drain, consider where it ends up. Surface water may not end up in the treatment plant but can discharged directly into the sea along with rainwater. 

You can check with your municipality where the wastewater ends up in your area.  

Good advice for car washing 

If you chose to wash your car at home, we have compiled some good advice: 

  • Choose a car shampoo without allergenic preservatives. Check the packaging for substance names containing –isothiazolinone. But note, that we found that not all producers list them as they should.
  • Always follow the instructions for use and preferably use gloves. 
  • Discard the used wash water into the toilet or sink. 

About the test

  • We have bought car shampoo either online or in physical stores on the Danish market. 

    We have checked whether the ingredient lists are available online, which is mandatory for washing and cleaning agents. 

    Only one car shampoo in the test has a mandatory ingredient list online. All other car shampoos in the test lack ingredient lists. 

    We have been in contact with the manufacturers or retailers to obtain the correct information. We have also notified all manufacturers of the test results. 

    However, we have not been able to obtain the information from several car shampoos in the test, even after repeated inquiries. 

    The test is a declaration test. This means that we have not conducted chemical analyses of the content. We have also checked whether there are differences between label information and information in the consumer data sheet (ingredient list). 

  • Isothiazolinones 

    16 out of 21 car shampoos in the test contain preservatives called isothiazolinones, which can cause allergies. They can also be problematic for the environment. 

    One of them is methylisothiazolinone, which in recent years more and more people have become allergic to. 

    When it is included in cleaning agents such as car shampoo, it must be listed on the label. The test showed that you can’t always rely on it appearing on the ingredient list. 

    We have found isothiazolinones in 16 products: 

    Benzisothiazolinone in 7 car shampoos 
    Methylisothiazolinone in 14 car shampoos 
    Methylchloroisothiazolinone in 9 car shampoos 

    Formaldehyde releasers 

    Other allergenic preservatives are also used in the form of formaldehyde releasers. 

    We have found various formaldehyde releasers in the test: 

    2-bromo-2-nitropropane-1,3-diol in 6 car shampoos 
    Benzylhemiformal in 1 car shampoo 
    Dimethylol glycol in 1 car shampoo 

    Other unwanted chemicals 

    • The substance group LAS in 5 car shampoos. LAS can be problematic for the environment. 
    • Perfume in 16 car shampoos. Perfume can cause allergies.
    • Sodium pyrithione in 2 car shampoos. The substance is allergenic and can be problematic for the environment. 
    • Diethanolamine in 1 car shampoo. The substance can damage the body's organs. 

    Difficult to find the list of ingredients 
    Only one car shampoo out of 21 car shampoos had the mandatory ingredient list available online.

    After extensive dialogue with manufacturers or retailers, it has been possible to obtain ingredient lists for an additional 18 car shampoos. However, there are some discrepancies between product labeling and ingredient lists on some of these products.

    For 2 car shampoos, we have not been able to obtain ingredient lists.