Preservative-Free TheraTears Liquid Gel TheraTears Liquid Gel is a thicker version of TheraTears that is perfect for nighttime, or for those who need a longer-lasting protective film during the day. Because TheraTears Liquid Gel is so long-lasting, it is formulated without a preservative so that unlike preserved gels, there never needs to be a concern regarding preservative-induced irritation. And because of its patented electrolyte balance, you will never experience the “electrolyte imbalance toxicity” you may get from other products.   More Info.