Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Emergency care is needed after a chemical exposure, a penetrating injury, or sudden major loss of vision.
After a chemical splash, begin rinsing the eye immediately with clean lukewarm water and continue while emergency help is arranged.
Do not delay rinsing to search for a specific eye solution.
And for anyone, someone who:
Arrange prompt medical assessment for eye pain, significant light sensitivity, persistent blurred or reduced vision, marked swelling, a feeling that something is stuck in the eye, or symptoms that worsen despite treatment.
Contact lens wearers with a painful, red eye should remove the lenses and seek prompt eye care because corneal infections can progress quickly.
Routine follow-up is appropriate when symptoms do not improve with reasonable allergen avoidance and properly selected nonprescription treatment, keep returning, interfere with daily activities, or make contact lens use difficult.
A clinician should also review symptoms that are mostly one-sided or accompanied by thick discharge, eyelid skin changes, or worsening dryness.
At follow-up, bring a list or photographs of all eye drops, medicines, cosmetics, and contact lens products being used.
This helps the clinician identify possible triggers and avoid duplicate ingredients.
Every sign above is quoted from the sofidex article on Allergic conjunctivitis. If you are not sure, err upward — it is always reasonable to be checked.