You need to use different solutions for each type of contact lenses. Use only solutions made for your type of lenses.
Gas permeable ("hard") lenses require special cleaners, soaking solutions, and wetting solutions. Wetting solutions are used to moisten the lenses while you wear them.
Soft lenses require many solutions including:
Solutions can contain different preservatives. If some lenses come in contact with more than one preservative, it can cause a chemical reaction. This can irritate your eye or discolor your contacts.
Some contacts can get discolored if you switch to a product that uses hydrogen peroxide to clean the lenses. Even switching from one brand of hydrogen peroxide cleaner to another can damage your lenses.
Soft contact lenses are the most likely to have problems. But problems can also happen with gas permeable contacts. For example, certain wetting or soaking solutions can make gas permeable lenses gummy.
You can avoid nearly all problems by following these guidelines: