NON-WATER-SOLUBLE CHEMISTRY KEEPS THE LOTION ON YOUR SKIN AND OUT OF THE WATER. NATURALLY HYDROPHOBIC (REPELS WATER). EXCEEDS INTERNATIONAL WATER RESISTANCE STANDARDS (FDA, AU, EU) .NO EYE-STING. NO GREASY RESIDUE. FRAGRANCE-FREE. GEAR SAFE - NO EQUIPMENT CONTAMINATION. High elevation skin exposure challenges the skin with extreme UV, and cold, dry air. This low moisture atmosphere environment robs the skin of water while cold dry winds chap and create windburn. UV intensity increases approximately 6% for every 1000 feet of elevation. Snow reflects up to 80% of UV. Combine the solar intensity or direct plus reflected UV and you can see why mountain environments present the highest UV exposure on earth. On snow, at 10,000 feet, the UV intensity is over 2.5 times that of sea level. Sol Sunguard Altitude SPF 40 is built to protect in the most extreme high mountain environments.