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Preservatives - undesirable effects
What are preservatives?
The use of preservatives is particularly important when the product packaging is designed for repeated use, which is common for cosmetic products intended for regular contact with air and skin.
In addition to cosmetic products, food, household and industrial products may also contain preservatives. Exposure can occur by:
- direct application / contact with the products to the skin or mucous membranes
- breathing airborne substances (e.g. by spray)
- eating food with added preservatives.
More than 150 different preservatives are approved for use in cosmetic products. Preservatives can be classified into three categories:
- UV light-absorbing compounds
The antimicrobial substances can be divided into:
- Formaldehyde donors (substances that release formaldehyde during degradation)
e.g. quaternium-15, diazolidinyl urea, imidazolidinyl urea, bronopol (2-bromo-2-nitropropane-1,3-diol) and DMDM hydantoin
- Non-formaldehyde-releasing substances
e.g. MCI/MI (methylchloroisothiazolinone/ methylisothiazolinone; also called Kathon), MDBGN (methyldibromo glutaronitrile), IPBC (iodopropynylbutylcarbamate) and parabenes.
What adverse effects can preservatives give?
Preservatives are a major cause of contact dermatitis. Areas such as the face, neck, hands and armpits are areas that are frequently exposed with respect to allergy from preservatives, but reactions in other sites may also occur. Preservatives can also cause other health problems such as contact urticaria and skin irritation.
A Danish study from 2010 examined allergy incidence to the most commonly used preservatives in patients who underwent allergy testing from 1985 to 2008 (Thyssen, 2008). Allergy to formaldehyde was found among 3.1%, MCI / MI among 1.8 % and diazolidinyl urea among 1.6 % of patients. The other substances studied were observed in 1 % or lower. In the period 2007-2008, the corresponding Norwegian figures for formaldehyde and MCI / MI were 3.1% and 2.0% respectively (Helsing, 2010).
Allergy incidence to the various preservatives varies within Europe. This may be due to different patterns of use of cosmetic products in different countries and national regulations for preservative use.
Over time, the proportion of the population that is allergic to a particular preservative changes, which probably reflects changes in the usage pattern and regulations.
If you are allergic to one or more preservatives it is essential to avoid products in which these ingredients are included. Read the ingredients list on cosmetic products you want to buy. As for formaldehyde allergy, it is also important to avoid using products containing formaldehyde donors. If in doubt whether a product contains substances you are allergic to, contact the supplier or retailer of the product.
Formaldehyde and formaldehyde donors
Formaldehyde is a cheap preservative with good antimicrobial efficacy. Its use in cosmetic products, however, has been significantly reduced because of its sensitising properties. Although the use of formaldehyde in cosmetic products has decreased over the past few years, the incidence of formaldehyde allergy remains high. This may be due to:
- the use of formaldehyde donors that release formaldehyde during degradation
- formaldehyde occurs as an impurity in some of the raw materials
- the release of formaldehyde from plastic containers
- the widespread use of formaldehyde in other products.
Quarternium-15, imidazolidinyl urea, diazolidinyl urea, bronopol and dimethyloldimethyl (DMDM) hydantoin are formaldehyde donors often used in cosmetic products. Quaternium-15 is the formaldehyde donor with the greatest potential to emit formaldehyde, and which in relation to frequency of use most often causes allergies. This substance is used in products such as hair care products, make-up, moisturisers and liquid soaps, sunscreens and shaving cream.
MCI / MI is both an irritant and an allergen. This substance often causes contact dermatitis on the hands and face. The cosmetic products that most often cause allergic contact dermatitis to MCI / MI include leave-on products (products intended to stay in prolonged contact). Widespread contact dermatitis can be seen by using moisturisers. MCI / MI in wet wipes has also been shown to cause dermatitis in intimate areas. In 2014, the EU decided that preservatives can only be used in rinse-off products (products intended to be removed after application).
Since the mid-1990s, IPBC has been approved for use in cosmetic products. As this substance is considered to have little risk for the development of allergy and to have low toxicity, the use of IPBC in cosmetic products has increased. However, figures from Germany, Switzerland and Austria show that the number of registered allergic reactions to IPBC increased by more than 10 % from 2002 to 2008 (Schnuch, 2011). In 2007, stricter restrictions were introduced for the use of IPBC. It is not allowed to be used in products for children under three-years-old, except in bath products and shampoo. IPBC cannot be used in leave-on products used on large areas such as body lotion.
Four types of parabens are commonly used; methyl paraben, ethyl paraben, propyl paraben and butyl paraben. Two or more parabens are often combined in a product since they amplify each other’s preservative effect (synergy). This group of substances has had a lot attention because of their potential endocrine-disrupting effects.
In 2011, EU's Scientific Committee of Consumer Safety concluded that methyl paraben, ethyl paraben, propyl paraben and butyl paraben can be used in cosmetic products for all age groups, except products for use in the nappy region for children under three years of age.
Given the widespread use of parabens in cosmetic products and the relatively low incidence of allergy, parabens do not constitute a big problem for the general population in terms of allergies. Cases of contact dermatitis have been reported but these are relatively rare.
Can preservatives be avoided?
Today, it is almost impossible to avoid contact with products containing preservatives. However, a continuous monitoring of the occurrence of various undesirable effects in the general population and a careful regulation of the use of preservatives which have been shown to have undesirable health effects is important to ensure that the cosmetic products are safe to use.