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This is complex but here it is.

1. HA sucks water out of the air and becomes wet. If you put dry HA on a dish, in about 30 minutes you would have a puddle of water. It is a very hygroscopic material, one which attracts moisture from the atmosphere. If not protected from contact with the atmosphere (by being stored under vacuum or under a dry gas) some hygroscopic materials will eventually attract so much water that they will form solutions.

2. Then this water wets or hydrates the outer skin proteins. This weakens the proteins and loosens the protective skin barrier.

The weak skin barrier allows bacteria, viruses, and allergens to pass through the skin. Often famous young actors in their late 20s have a very spotted skin (you often see this on a large screen) from skin barrier damage from heavy use of make up and make up removers.

3. The wet proteins slow keratin production. The signal for the skin to send up new keratinocytes to the surface is a dryness in the proteins in the top of the skin. So skin is replaced slower and damage accumulates.

4. Many years ago, women used Cold Creams to keep their faces moist when they went to bed. If you have seen "I Love Lucy" or old movies, you have seem women with these white creams all over their face. But they ended up with horrible wrinkles as time went by because their skin had been keep too wet.

5. There is the idea of a limited cell life but many cell biologists doubt if this is correct. No one knows how long cells can live because very long cell culture experiments are very expensive.

The body also makes stem cells - even in adults - that can keep setting up new cell lines.