If your diet doesn't include a regular intake of oily fish, then it is possible that you could have a fatty acid deficiency. Signs that your body isn't being supplied with high enough levels of Omega 3 can include:
Skin, Hair & Nail Problems
Dry Skin
dry flaky scalp
Dry Hair
brittle, or soft peeling nails
"Goose pimple" type skin, particularly on the upper arms or top of the legs.
Tendency towards allergies and skin sensitivity
Attention Problems
Difficulty in seeing jobs through to the end
Distracted easily
Difficulty seeing tasks through to completion
Attention is difficult to sustain
Doesn't seem to listen to others around them
Forgetful in day to day activity
Can make careless mistakes
Eyesight Problems
Poor night-time vision
Sensitive to bright light
Headaches
Eye-strain
Loses place on page when reading
Words or letters move around when reading
Personality Problems
Tendency to become frustrated
Tendency to be oversensitive & emotional
Tendency to overdo and over-react to situations and subsequently become over-tired
Tendency to be melancholic
If some of these sound all too familiar and you know that you're not eating regular amounts of Omega 3 (through fish or other sources) then you should consider increasing your intake of healthy Omega-3 oils. If you don't like fish, try taking a good quality supplement.
N.B. Some of these symptoms can also be a sign of an underlying illnesses for which you should seek advice from your GP.