Introduction
Eyes can become red from many different causes, allergies or infections. This is called conjunctivitis.

Symptoms
The inside of the eyelid is red, and the redness often spreads onto the whites of the eyes. Infections are due to either viruses or skin bacteria. Red and/or itchy eyes can also be caused by an allergy to things such as pollen (from grass, plants and trees), hay fever and increasingly-air pollution. Eyes also redden if something gets into the eye. Looking at a welding arc or ultraviolet light without protecting the eyes is dangerous (arc eye). Red and painful eyes can also be caused by an eye infection deep inside the eye.

Treatment: What you can do for yourself
Always be sure to wear protective goggles when using power tools or when under a sunray lamp. If a substance gets into your eyes and is not an acid or other caustic substance then try repeated rinsing with lukewarm water.

**********IF A CAUSTIC SUBSTANCE SUCH AS ACID GETS INTO THE EYE, RINSE THE EYE AND GO STRAIGHT TO YOUR LOCAL CASUALTY DEPARTMENT ************

For any eye infections or soreness
Cleanse the eyes with water that has been boiled and cooled. Often the eyelashes become stuck together, soak away the crusts using moist cotton wool. It is quite safe to cleanse the inside of the lower eyelid. Pull the eyelid down slightly and wipe the cotton wool from the side towards the nose.

Contact your doctor if:

• The eyes are discharging pus
• They are not better after 2 days

Contact your doctor immediately if:

• You think there is something in the eye and you cannot rinse it out for yourself
• The eye is painful. 

http://patient.info/health/infective-conjunctivitis-leaflet