Soft lenses, especially, must never be used with hard lens solutions. When travelling or sunbathing, be careful not to fall asleep with your lenses in, unless they are designed for this.
Swimming is unwise with gas-permeable hard lenses because of the risk of loss.
Soft lenses are often better, but still be careful of loss. Also, if chlorine is absorbed into the lenses it may cause stinging and red eyes. If possible, avoid wearing lenses for long flights because of the dry atmosphere on the plane. If you decide not to wear your lenses while travelling, keep them in your hand luggage in case your main baggage goes astray. Keep spare lenses in a separate place.