Allergies affect over 20% of the general population and are on the rise in many developed countries. The specific reason for the increasing prevalence of allergies has not been determined; some believe it is due to the effects of pollution in urban areas while others consider that modern lifestyles don’t allow for enough childhood exposure to allergens to become acclimated to them.
Allergies can take many forms, affecting various organs or tissues. Ocular allergies are among the most bothersome forms of allergic reaction. The characteristic signs and symptoms of ocular allergies include:
• Watery eyes
• Swelling of the eyes and eyelids
Ocular allergies are often accompanied by allergic rhinitis (nasal symptoms). This is partly due to the fact that the eyes and nose are so closely connected by the tear ducts; substances that enter the eye can then flow downward into the nose. Symptoms include:
• Runny nose
Eye allergies are no different than allergies that affect your sinuses, nose or lungs. When an allergen comes in contact with your eyes, your body releases histamine – a chemical produced in reaction to a substance that the immune system can’t tolerate. Special cells called mast cells make histamine. These cells are present throughout the body but are highly concentrated in the eyes. Location of allergy symptoms depends somewhat on where the allergen has come into contact with your body. Ocular allergens tend to be airborne (as are most other allergens).
The most frequent allergic triggers include:
• Pet hair or dander
• Some medicines
Some triggers irritate the eyes but are not true allergies:
• Cigarette smoke
• Diesel Exhaust
The Eyes’ Response To Ocular Allergens
When exposed to these allergens, the response in the eye is nearly immediate:
• First, itching sets in and can become persistent and extremely bothersome if exposure to the allergen is continued.
• Shortly after itching, redness of the eyes follows and can last somewhat longer, as the blood vessels of the eye are slower to recover.
• The swelling of the eyes and eyelids comes to its peak later than the itching, as swelling is also caused by the blood vessels letting fluids out into the tissue around them. Swelling is the sign of ocular allergies slowest to disappear, due to the time it takes for the displaced fluid to be removed.
• The itching can be considered the most uncomfortable symptom, whereas the swelling and redness are most bothersome in terms of appearance.