They do damage your own nails but are strong, hard and long. You can avoid fungal infections by maintaining the acrylics or silk wraps. If they separate and water gets under them, you will be in trouble. Also, remove them periodically and give your nails a break (no pun intended).
Before I went that route, I would try clear nail polish. There are some that strenghten the nail and "feed" it as well.
I knew a woman who NEVER removed her fake nails. One day she turned her hand over and I nearly lost it. She had green growing under every nail. She told me she soaked her hands in bleach when it smelled really bad - ARGHHHHH!