Fish oil contains essential fatty acids. It has been shown to be good for heart health, reduce inflammation and contains antioxidants to help fight illness. But fish oil may also help your skin. Food rich in omega 3 and omega 6 fatty acids include walnuts, flaxseed, salmon, mackerel, anchovies and tuna. Many people, however, don't get enough omega 3 fatty acid from their diet and choose to take fish oil supplements.
Some of the benefits of fish oil for your skin include:
According to Discovery Health, there have not been any scientific studies proving that foods high in omega 3 fatty acids relieve dry skin, some studies suggest that they are beneficial to skin health.  An article in The Huffington Post by Dr. Robert Tornambe, "Fish Oil for Your Face? The New Anti-Aging Phenomenon," fish oil help to "bolster the skin cell membrane of the epidermis."  The epidermis is the outer layer of your skin. As you age, this layer thins and holds less moisture. Omega 3 helps keep the epidermis healthy, allowing skin cells to better hold water. This keeps your skin hydrated and softer.
Reducing UV Skin Damage
In addition to helping increase moisture in your skin, omega 3 may also reduce skin damage, including cancer cells, from UV rays. A study in the Journal of Lipid Research in 2005 showed that omega 3 actually blocks UV-induced enzymes which damage the collagen in our skin. Damage from overexposure to the sun causes premature aging and wrinkles. A diet with omega 3 may help to improve the look of your skin by decreasing the effects of UV rays.
Acne occurs when your skin produces excess oil, causing bacteria under the skin. This causes inflammation. Omega 3 has been shown to help reduce inflammation, which will decrease acne breakouts. Fish oil may help those with mild or moderate acne. For acne that is not improved or worsens with the use of fish oil, you should see your dermatologist.
Fish oil has also been used to help in treating skin conditions such as atopic dermatitis and psoriasis. Some research has shown that while fish oil can help reduce symptoms of psoriasis, other studies have not found the same results. Another study found that those taking fish oil on a daily basis had decreased symptoms of eczema over a 12 week period of time. 
As with any supplements, it is important to talk with your doctor before taking. Your doctor should be able to recommend a starting dosage and explain how often you should increase your daily dosage of fish oil supplements. You should also talk with your doctor about possible side effects or interference with any other medication you are taking.
 "Can My Diet Affect the Moisture of My Skin?" Date Unknown, Sarah Jourdain, Discovery Fit and Health
 "Dermatitis," 2011, A.D.A.M Medical Encyclopedia
 "Fish Oil for Your Face? The New Anti-Aging Phenomenon," 2011, Oct 17, Robert Tornambe, M.D., The Huffington Post