The causes might be due to Bacterial, Viral or Environmental.
Conjunctivitis is generally not a serious problem. But it is important to consult your doctor. Bacterial conjunctivitis is generally treated with antibiotic drops or ointment. Like a cold, viral conjunctivitis will usually go away on its own, even without treatment. But eye-drops are often prescribed to help control the symptoms. Conjunctivitis caused by viruses does not respond to antibiotics. You can soothe the discomfort of viral or bacterial conjunctivitis by applying warm compresses (clean cloths soaked in warm water) to your closed eyes.