In short:
Parabens are esters of salts and 4-hydroxybenzoic acid. The pharmaceutical, cosmetic, and food industries use them to a large extent for preservation. NO, parabens in cosmetics are not harmful. In order for cosmetic products containing water (creams, emulsions, lotions, tonics, milks...) to remain safe from bacteria and mould for more than a few days, they need to have added preservatives and antioxidants. We can probably all agree that you would not want to apply a mouldy cosmetic product to your skin.
In recent years you have probably heard a lot about parabens and their uses when mentioned by the media as "dangerous and unwanted" substances in cosmetics. Since then, more and more people have decided to make cosmetics that do not contain parabens, even though they do not know what parabens are, how they work, or why they are toxic. The general public's opinion is that parabens are synthetic, unnatural, and dangerous molecules that can endanger our health and interfere with our balance of hormones. This, however, is incorrect!
Parabens should be as much as 10 000 times weaker than natural phytoestrogens found in food. They are derived from hydroxybenzoic acid, a substance that naturally occurs in some fruits. Methylparaben, for example, is a completely natural substance found in blueberries.
Parabens have been used as preservatives in cosmetics for an extremely long time, and during this time no side effects have been reported. They remain one of the safest, most effective, and best researched preservatives on the market. So why are people so happy to grab for products with "Paraben free" on the label? The answer is that this has been an exceptionally successful marketing strategy by the producers of these products, despite the fact that they use less-researched (and thus possibly more dangerous) preservatives. The lack of knowledge among the public on this matter also contributes to this success. Parabens in cosmetics (methyl-, ethyl-, propyl-) are completely safe, and thus "paraben free" products are just a clever marketing strategy.
Keep in mind that products that do not contain parabens may contain some very dangerous chemicals to maintain their quality.