Eye allergies (allergic conjunctivitis) happen when your immune system overreacts to usually harmless substances that get into or around your eyes.

Quick Scoop

When an allergen touches the surface of your eye, immune cells release chemicals like histamine, which make the tiny blood vessels in your eyes leak and swell. That’s what causes the classic red, itchy, watery, swollen eyes many people call “eye allergies.”

Main Causes: What Sets Them Off

1. Outdoor allergens (very common)

These usually drive seasonal eye allergies, often worse in spring and fall.

  • Pollen from grass, trees, and weeds.
  • Mold spores in damp outdoor areas, piles of leaves, or humid environments.

You may notice flare-ups when:

  • You’re outside on high‑pollen days.
  • It’s windy and dry rather than rainy and cool.

2. Indoor allergens (year‑round triggers)

These tend to cause perennial (all‑year) eye allergies.

  • Dust mites in bedding, pillows, carpets, and upholstered furniture.
  • Pet dander and dried saliva from cats, dogs, and other furry animals.
  • Indoor mold in bathrooms, basements, kitchens, or around leaks.

Many people wake up with puffy, itchy eyes because of dust mites or pet dander in the bedroom.

3. Irritants that mimic allergies

These may not be “true” allergies but can cause very similar eye redness and irritation.

  • Cigarette smoke and secondhand smoke.
  • Strong perfumes, sprays, and scented products.
  • Air pollution and diesel exhaust.
  • Chlorine in swimming pools and some cleaning chemicals.

Your immune system may not be doing a classic allergic reaction, but your eyes still get inflamed and uncomfortable.

4. Contacts, solutions, and eye products

The stuff you put on or near your eyes can also cause trouble.

  • Contact lenses themselves, especially when worn for long periods or not cleaned properly.
  • Proteins from your tears that build up on the lens surface (can lead to giant papillary conjunctivitis).
  • Contact lens solutions or eye drops that your immune system becomes sensitive to.
  • Makeup and cosmetics (eyeliner, mascara, eyeshadow, creams) used around the eyes.

In contact allergic conjunctivitis, the inner eyelid and surface of the eye get inflamed and cause redness, itching, mucus discharge, and lens discomfort.

5. Other medical/immune reactions

A few less common but important causes and contributors:

  • Atopic tendency (people who also have eczema, asthma, or nasal allergies are more prone to eye allergies).
  • Rare chronic eye allergy types (like vernal or atopic keratoconjunctivitis) which are usually more severe and need specialist care.
  • Some medications and eye drops that your body recognizes as allergens.

In all of these, your immune system is primed to “overreact” to triggers that other people may tolerate easily.

What Actually Happens in Your Eyes

When an allergen hits your eye surface:

  1. Your immune system has antibodies attached to mast cells in the eye tissues.
  1. The allergen binds to those antibodies and activates the mast cells.
  1. Mast cells release histamine and other chemicals.
  1. Histamine makes blood vessels leaky and nerves more sensitive, so you feel:
    • Itching
    • Redness
    • Burning
    • Watery discharge

This is why antihistamine eye drops often help—they block some of that histamine activity.

Quick reality check: allergy vs infection

A “pink eye” look doesn’t always mean allergy.

  • Allergy: itchy, both eyes, clear watery discharge, often with sneezing or nasal allergies at the same time.
  • Infection: more crusty/yellow discharge, may affect one eye first, can be contagious if viral or bacterial.

Because treatments differ, persistent or severe symptoms should be checked by an eye doctor or allergy specialist.

Why this is a trending topic

With rising pollen counts in many regions and more people using contact lenses and cosmetics every day, eye allergy complaints have become increasingly common in recent years. Telehealth and online forums are full of people asking whether their “red, itchy eyes” are from screens, allergies, or infections, and the answer is often some mix of allergens plus modern lifestyle irritants.

TL;DR: Eye allergies are caused by your immune system overreacting to allergens like pollen, dust mites, pet dander, and mold, plus triggers such as smoke, perfumes, contacts, and some cosmetics that inflame the surface of your eyes.

Information gathered from public forums or data available on the internet and portrayed here.