They claim to hold the hands of time at bay by smoothing wrinkles and plumping up skin。

　　But expensive collagen creams are a waste of money, scientists said today. They say that the collagen molecules in the enticing-sounding lotions and potions are so large that very few make it through the skin。

　　Richard Guy, professor of pharmaceutical sciences at the University of Bath, said: 'The idea created by many of these products is that collagen can get through the upper layers of skin and reinforce our own natural collagen, but this is preposterous。

　　"The simple fact is that collagen is a huge molecule and the skin is designed to keep such substances out."

　　As a result, they sit on the surface of the face until they are rubbed off or washed away. Jonathan Hadgraft, professor of biophysical chemistry at the University of London's school of pharmacy, said: 'There is a popular belief that about 60 per cent of such creams is absorbed through the skin but the reality is that most of it just stays on the skin。

　　"If it did penetrate the skin and get into the blood, it would have to be classed as a medicine."

　　Collagen is a protein that gives skin its strength and elasticity. With the amount we make falling as we age, the protein has become a key ingredient of many creams that claim to rejuvenate the skin and smooth away wrinkles。

　　A spokesman for L'Oreal said the firm includes dehydrated collagen spheres in some of its products. 'When combined with other ingredients and applied to the skin's surface, the spheres have been independently proven to expand by up to nine times and create a plumped, hydrating and smoothing effect of the skin's surface.'

　　Chris Flower, of the Cosmetics, Toiletry and Perfumery Association said: "Manufacturers are very careful about the exact wording of the claims they make, but here is a risk of customers forming the wrong impression from some packaging and advertising."

　　一般认为，骨胶原抗皱面霜能除皱唤肤，防止衰老。然而科学家却表示，骨胶原面霜虽然价格不菲，但并无实在功效，因为这些让人眼花缭乱的护肤品所含的骨胶原分子太大，不能透过皮肤而真正被吸收。

　　巴斯大学药物学教授理查德•盖伊称："许多产品都宣称骨胶原可以渗透浅层皮肤，补充人体骨胶原数量。纯属无稽之谈，因为骨胶原分子太大，皮肤结构会直接把大分子物质隔离在外。"

　　结果是骨胶原只会附着在脸部皮肤表面，一擦、一洗就掉。伦敦大学药学院生物物理化学教授乔纳森•哈德格拉斐特说："人们普遍认为60%的面霜都会被皮肤吸收，然而事实却是大部分都只附着在表皮。如果真能渗透皮肤、进入血液，就应归为药物了。"

　　骨胶原是一种能增强皮肤弹性的蛋白质。随着年龄的增长，骨胶原含量会慢慢降低，于是许多面霜便鼓吹这一成分能抚平皱纹，恢复肌肤活力。

　　欧莱雅的一位发言称该公司部分产品含有脱水骨胶原球，"使用时，这些球体在其他成分作用下，会自动膨胀成原来的9倍大，从而抚平皱纹，补充水分。"

　　英国化妆品盥洗用品及香水协会(CTPA)的克里斯•弗劳尔说："制造商们措辞严谨，有时候可能在包装和广告上误导消费者。"