An eye allergy is a disorder of the immune system that affects the eye, causing an overreaction to certain environmental irritants. It is relatively common and only rarely threatens vision in those affected.
Eye allergies are quite common in most people. They occur when the immune system gets sensitized to something (an irritant) in the environment. The body fights off by producing histamine and as a result, causes inflammation to the eyes. The irritant typically does not affect other people.
The allergies can be classified into six major types:
- Seasonal allergic conjunctivitis (SAC)
This type of allergy appears during specific times of the year. It occurs in spring, summer or fall when there are pollens in the air. People with this type of allergy will have dark circles under the eye. The symptoms also go with those of allergic rhinitis, e.g., sneezing, nasal congestion and runny nose.
- Perennial allergic conjunctivitis (PAC)
Allergies, in this case, are present all year long. The symptoms are like those of seasonal allergic conjunctivitis but milder. The reactions mostly occur due to other irritants besides pollen.
- Vernal keratoconjunctivitis (VKC)
It is considered a more severe form of allergy. It may occur all year round but gets worse during hot and dry seasons. It is majorly seen in the younger males and is associated with a family history of atopy.
- Atopic keratoconjunctivitis (AKC)
Similar to vernal keratoconjunctivitis, this type of allergy is associated with a personal or family history of atopy. The difference in the two is that while vernal conjunctivitis affects the upper tarsus of the cornea, atopic conjunctivitis affects the lower part. Atopic conjunctivitis is also prevalent in older groups, is more chronic and may result in corneal and conjunctival scarring.
- Contact allergic conjunctivitis
This kind of allergy results from contact of the eyes with specific allergens. Allergens such as eye drops, cosmetics, among others.
- Giant papillary conjunctivitis
It is also referred to as contact lens-associated papillary conjunctivitis. It comes about from wearing contact lenses. Individuals develop papules in the upper lining of the inner eyelid.
- Seasonal allergic conjunctivitis
- Perennial allergic conjunctivitis
- Vernal keratoconjunctivitis
- Atopic keratoconjunctivitis
- Contact allergic conjunctivitis
- Giant papillary conjunctivitis/Contact lens-associated papillary conjunctivitis
Causes and Risk Factors
The cause of eye allergies is based on the type. However, the triggers can be broadly categorized as follows:
Outdoor allergens; These include pollen from plants, weeds, trees and grass.
Indoor allergens; These are such as dust mites, mold and pet dander.
Irritants; They include perfume, cigarette smoke, and fuel exhaust.
Risk factors for eye allergies include:
Exposure to allergens
Personal or family history of allergies such as allergic rhinitis, or atopic conditions such as eczema, asthma or dermatitis
Hot and dry environmental conditions
Signs & Symptoms
The primary signs and symptoms include:
- Burning sensation
- Clear watery discharge from the eyes
In VKC and AKC, there may also be a production of thick mucus which may cause the eyelids to stick together.
Eye allergies present symptoms similar to those of other eye diseases. It is therefore imperative to rule out any other condition.
The diagnosis may involve scraping off of the conjunctival surface to check for certain types of white blood cells using a microscope. The microscope exam could also show swollen blood vessels on the ocular surface.
In eye allergies, treatment is aimed at countering the reaction of the eyes or relieving symptoms.
Eye allergies can be managed using the following:
- Artificial tears (tear substitutes)
- Decongestant eye drops
- Oral antihistamines
The antihistamine drugs and decongestant eye drops may worsen symptoms over time. They should, therefore, be used with a prescription from an eye care professional.
In the severe case of cornea shield ulcers, an eye care professional may indicate a superficial keratectomy.
The prognosis for eye allergies is good. The condition has no long-term effect on health. In fewer VKC and AKC cases, corneal damage and vision loss may occur without treatment.
Preventive measures include:
- Avoid certain environmental stimulants, e.g., smoke
- Wear sunglasses when outdoors to prevent pollen from getting into the eyes
- Close windows during high pollen periods
- Wash hands after touching pets
- Use mite-proof bed covers