以下是引用tasteofair在2006-1-27 20:30:00的发言:网上偶尔看到的, 贴个我看过的网站:http://www.soapnaturally.org/naturalskincare/preservatives.html
MRH上有卖这个grape fruit extract,也说起防腐作用。
Preservatives
Preservatives are substances that kill bacteria and fungi (or at the very minimum make it very difficult for "living things" to survive), and have no effect on the shelf life of the oils. Bacteria, fungi, yeast and other potentially dangerous microorganisms typically avoid waterless compounds (such as balms, salves, pomades and oil-only blends) and also substances with a relatively high pH (such as soap), but thrive in humid environments. For this reason, soaps and oil-based skin care applications do not need preservatives - but unlike these, creams, lotions and any other compound where water is present require adding a preservative if the shelf life and integrity of the product need to be extended further than 2 or 3 weeks.
It is important to understand that the efficacy of preservatives relies, by definition, on their ability to kill live cells; in other words, their toxicity is an unavoidable component of their reason of being. A number of natural extracts, plants and essential oils contain substances that have the power to effectively kill bacteria, yeast and fungi; however, in many cases these substances are or can be toxic for humans, too. A typical example are citrus or grapefruit seed extracts: although these have natural antimicrobial properties, some of their constituents are thought to be responsible for life-threatening hormonal imbalances. Also, citrus seed extracts are not approved for cosmetic use in Europe and in Japan, and are therefore not an option in those countries.
In the last few months, a new type of natural preservative has appeared on the market. Similar in look, feel and scent to an essential oil blend, and made by combining active fractions of essential oils, this new preservative system seems to have the potential to address the needs of those skin care manufacturers who want their products to be completely natural - yet, being such a new product, some time might be required before its efficacy and possible contraindications are proven once for all.
Among the synthetic preservatives available for handmade skin care products, paraben-based systems seem to be particularly controversial. A large number of articles, books and so-called "expert" opinions point to paraben-based preservative systems as being responsible for the "skin unfriendliness" of many industrial products. However, in-depth medical and scientifical researches show that paraben-based preservatives are by far less dangerous, both for the skin, and for the environment, than most other types of preservatives, such as for instance those that fall into the "formaldehyde donors" category.
刚才研究了一下, 很多婴儿用品里都用这个做防腐剂, 过敏性比较小.