Propylparaben is one of a family of chemicals known as parabens that are compounds of parahydroxybenzoic acid. The others area methyl-, ethyl-, and butylparaben. Although these compounds occur naturally — in some plants, for example — they are manufactured synthetically, and used mainly as preservatives and antimicrobials in cosmetics, foods and pharmaceuticals. Propylparaben is the form most commonly used. The compound has very low toxicity, but there is concern that it could play a role in the development of breast cancer, among other things.
Properties and Uses
Cosmetics, pharmaceuticals, and foods can all spoil, due to the action of bacteria and fungi, if they do not contain a preservative or antimicrobial agent. Studies have shown propylparaben to be effective at low concentrations. It is particularly good at killing, or preventing the growth of, fungi, and works well across the range of acidities that includes most products intended for external or internal use. This, combined with its apparent lack of toxicity to humans and other mammals, and its low cost of manufacture, has led to its widespread use in a variety of products.
The compound is used extensively in the cosmetics industry, and is considered safe at concentrations of up to 25%. It has become the preservative of choice, especially for cosmetics that are water-based — such as moisturizers, shampoos, shower cleansers, conditioners, and sunscreens. Lipsticks, foundations, mascaras, and eye shadows may also contain it.
In the pharmaceutical industry, propylparaben is a common preservative for certain drugs. As a result, it is can be absorbed humans in several ways: injections, orally, or through suppositories. Since these uses involve the compound being taken internally, it is not normally found in concentrations exceeding 1%. The same applies to its use in foods.
Effects on Humans
Testing for acute or chronic toxic effects has indicated that propylparaben has low toxicity for mammals. It can be mildly irritating to the skin, and there are reports of allergic reactions, but it is not thought to directly cause any other ill effects. It is easily absorbed into the system when taken orally, but is quickly broken down, and does not normally appear to accumulate in the body.
The main concern about this substance is that, like other parabens, it can mimic, to some extent, the action of the female hormone, estrogen. Although it is essential to female development, early exposure to the hormone has been associated with breast cancer, and estrogen-suppressing drugs are used in treatment of the disease. There appears to be no direct evidence linking parabens with cancer, but a number of studies have been conducted that have created fear in some consumers.
In one study, a group of British researchers tested tissue samples that were taken from women who had cancerous breast tumors. The researchers found traces of parabens in the lumps of all 20 women. This has caused some people to wonder whether these chemicals caused the cancer.
Other examples that cause concern include a September 2008 study of 20 girls between the ages of 14 and 19. The girls used multiple cosmetics products every day — from moisturizers to deodorants to make-up. In that study, propylparaben was found in every girl.
It is possible that parabens may also affect men. In one study on male rats fed these chemicals at various doses, it was found that testosterone production decreased in proportion to the dose. As of 2013, there is no clear evidence of any adverse effects from these substances on humans, and research into them is ongoing, but many people are taking a “better safe than sorry” approach and trying to avoid products containing these chemicals.
Since there is increased awareness of these compounds, and concern about their possible effects, some cosmetics manufacturers, particularly those that are organic in nature, are looking for alternative ways to prevent their products from spoiling or to inhibit microbial growth. Some may simply settle for shorter shelf lives, while other manufacturers are looking into other preservatives. Until more information is available, the safest course may be to limit exposure to parabens.