Why do we get itchy eyes?

Itchy eyes are among one of the most common symptoms for those with allergies, especially in the warmer months of the year when dust, pollen, and grass are increasingly prevalent. The chemical in the body that leads to itchy eyes is histamine, so that’s why antihistamine pills or eye drops are so effective in easing allergy symptoms.

Without antihistamines in the body, histamine has full range to produce all the most frustrating systems those with allergies dread – especially in the eyes. While blinking is often successful in preventing foreign molecules from entering the eye, the foreign molecule will sometimes surpass the eyelid. If the individual happens to be allergic to the foreign molecule, the body will cue a sequence of defense
mechanisms. Mast cells, which are the eyes’ immune cells, bind to the allergenic molecules and treat them like pathogens. The mast cells then release histamine in a process called degranulation, causing irritation in the eyes. The release of histamine may affect other parts of the body, including the upper-respiratory system (congestion, runny nose, sinus pain, etc.) and the skin (rashes and dryness) in addition to the eyes.

While researchers are still not completely clear on how histamines specifically activate itchiness, they believe the itching feeling is meant to promote scratching to dislodge any foreign/allergenic substances from the body. Histamine levels reach their highest point roughly 5 minutes following contact with the allergen, but unfortunately, itchy eyes may last longer than that. The second release of histamine occurs between 6 and 72 hours after the first release in attempt to continue fighting off the allergen. This second release is what makes itchy
eyes so annoying – the sensation can last for so long!

Source: Medical News Today

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