This info is from: http://www.whfoods.com/genpage.php?tname=foodspice&dbid=42
The flesh of cucumbers is primarily composed of water but also contains ascorbic acid (vitamin C) and caffeic acid, both of which help soothe skin irritations and reduce swelling. Cucumbers' hard skin is rich in fiber and contains a variety of beneficial minerals including silica, potassium and magnesium.
A Radiant Complexion
The silica in cucumber is an essential component of healthy connective tissue, which includes muscles, tendons, ligaments, cartilage, and bone. Cucumber juice is often recommended as a source of silica to improve the complexion and health of the skin, plus cucumber's high water content makes it naturally hydrating a must for glowing skin. Cucumbers are also used topically for various types of skin problems, including swelling under the eyes and sunburn. Two compounds in cucumbers, ascorbic acid and caffeic acid, prevent water retention, which may explain why cucumbers applied topically are often helpful for swollen eyes, burns and dermatitis.
An Easy Way to Increase Your Consumption of Both Fiber and Water
Trying to get adequate dietary fiber on a daily basis is a challenge for many Americans. Adding a crunchy cool cucumber to your salads is an especially good way to increase your fiber intake because cucumber comes naturally prepackaged with the extra fluid you need when consuming more fiber. Plus, you get the added bonus of vitamin C, silica, potassium and magnesium.
High Blood Pressure? Cucumber Can Help You Cool Down
When people who participated in the DASH (Dietary Approaches to Stop Hypertension) Study added foods high in potassium, magnesium and fiber, their blood pressure dropped to healthier levels. Those people in the study who ate a diet rich in these compounds in addition to the other foods on this diet (low fat dairy foods, seafood, lean meat and poultry) lowered their blood pressure by 5.5 points (systolic) over 3.0 points (diastolic).