Well, generally speaking, it is very common for many people to have allergic to contacts, for contacts are made of plastic material. And these plastic materials can just be the irritants in your eyes, leading to some eye problems, such as eye allergy. Also, if someone do not have clean the hand, it will just carry some allergy into your eyes, leading to allergy to eyes too. And at that time, your eyes will feel uncomfortable, and also redness in your eyes will occur. In some cases, burning eyes may be possible too. So just be careful about it.
Ok, it is true that some people cannot wear contact lenses, partly because they are allergic to those lenses, partly because they have got some infections like trachoma. Thus, you gotta make sure you are ok with such contact lenses. Then, if there are no irritative reactions on your eyes, perhaps you are ok with them and are of course good to go. But be aware that such lenses may be negative to your eye health so you should make good and proper use of them.
If you are allergic to contact lenses, your eyes will easily complicated with inflammation, such as eye itching, redness and swelling when you first time to wear it. On the other hand, there are several people are not suitable for wear contact lenses. The first, somebody who often suffer from colds, because cold often accompanied with retinitis. Second, somebody who have eye disease, for example, such as keratitis and conjunctivitis, glaucoma, dry eyes. Third, the women who during pregnancy also recommended not to wear contact lenses.