• Itching, redness and conjunctival oedema in both eyes are typical symptoms.
• Acute allergic, seasonal, perennial and atopic conjunctivitis are the most common types of allergic eye inflammation.
• Atopic keratoconjunctivitis is more common in patients with previously diagnosed atopic dermatitis.
• Mast cell stabilizer drops used for a sufficiently long time and antihistamine tablets or drops, as necessary, are often sufficient treatment. Moisturizing drops may also alleviate the symptoms.
• Patients with allergic eye inflammation with severe or prolonged symptoms, as well as those whose diagnosis needs to be specified further, should be referred to an ophthalmologist.

• One in three people are estimated to have some allergic disease, and more than 40% of these have eye symptoms.
• Allergic conjunctivitis is estimated to occur in 20% of the population.

Acute allergic conjunctivitis

• Caused by cat dander, for example
• Symptoms usually occur in both eyes. They develop quickly, as soon as within 30 minutes of exposure, and often subside within 24 hours after exposure.
• Itching, redness and watering of the eyes, photophobia, conjunctival oedema (chemosis)
• Lid swelling and lid eczema

Seasonal allergic conjunctivitis (SAC)

• Symptoms caused by tree or grass pollen, for example, and develop within several days or weeks.
• There is often severe itching
• Redness and watering of the eyes, photophobia, conjunctival oedema (chemosis)
• Sometimes mild eczema on the eyelids

Perennial allergic conjunctivitis (PAC)

• Symptoms often occur throughout the year and are milder than in acute or seasonal inflammation, often caused by indoor allergens, such as dust mites, animal dander or mould
• The symptoms often vary, with intermittent exacerbations and periods of milder symptoms
• Itching, bloodshot conjunctiva, watering, lid oedema

Atopic keratoconjunctivitis

• Often severe itching, which may lead to intensive rubbing of the eyes
• Red eyes, watery discharge, photophobia and foreign body sensation
• Often significant effects on lid skin (thickening, swelling), dermatitis and periocular erythema

Vernal keratoconjunctivitis (VKC)

• Itchy eyes, tearing, foreign body sensation, pain
• Mucous discharge
• Blurred vision
• Giant papillae on the inside of the upper eyelid
• Peak incidence in 7–12-year-old boys
• A rarer form of allergy; refer to an ophthalmologist

Giant papillary conjunctivitis (GPC)

• Inflammatory reaction of the eyelid to the use of hard contact lenses, for example, or other mechanical irritation
• Begins with mild itching or irritation
• Clear discharge, as the condition progresses often mostly in the morning
• Intensive itching as the condition continues
• Enlarged papillae on the inside of the upper eyelid
  • At first, about 0.3 mm, and as the disease progresses, up to 1–2 mm

Non-allergic eosinophilic conjunctivitis (NAEC)

• A common but underdiagnosed condition resembling allergic eye inflammation
• Often associated with dry eyes
• Similar to non-allergic eosinophilic rhinitis
• Can be diagnosed from a conjunctival exfoliative sample. In addition, dry eye and allergy tests should be performed.
• Diagnostic criteria of NAEC
  • Conjunctivitis lasting for at least one month
  • Signs of infection
  • No atopic allergy (results of skin prick tests negative, no allergen-specific IgE antibodies in serum)
  • Conjunctival cytology gives at least one + for eosinophils (on a scale from + to ++++)

• Allergic conjunctivitis is diagnosed based on typical symptoms and findings (see above) and exposure history.
• Allergy tests support the diagnosis. Microbial samples can be taken to exclude other causes.

GP workup

• Visual acuity, intraocular pressure, fluorescein staining
• Schirmer’s test for dry eyes
• Allergy tests: skin prick tests, IgE tests
• Microbial samples (bacterial and viral)

Further ophthalmological workup

• Serum IgE tests if these have not already been performed
• Eye challenge test, if desensitization is considered or an occupational disease is suspected
• Conjunctival brush cytology
• Biomicroscopy of the eye

• Dry eyes (Dry eye syndrome)
• Bacterial or viral conjunctivitis (Conjunctivitis)
• Non-allergic blepharitis (Blepharitis)
• Ocular rosacea (Rosacea)
• Toxic conjunctivitis
• Malposition of the eyelid (particularly entropion with eyelashes rubbing against the eye surface) (Entropion and ectropion)
• Lid margin tumour
• Conjunctival tumour
• See also the article on Red eye (Red eye)

Acute allergic conjunctivitis

• Concomitant effective treatment of allergic rhinitis and asthma is essential.
• Antihistamine tablets
• Topical mast cell stabilizer (cromoglycate or lodoxamide drops) alone or combined with an antihistamine
• In addition, antihistamine drops, as necessary (azelastine, emedastine, levocabastine, ketotifen)
• For severe symptoms, brief treatment with topical glucocorticoid drops prescribed by an ophthalmologist

Seasonal allergic conjunctivitis

• Mast cell stabilizer drops
  • It is often useful to start medication one week before the pollen season.
• Antihistamine tablets and, additionally, antihistamine drops, as necessary
• A dual action olopatadine product (histamine antagonist and mast cell inhibitor), as necessary
• If there are disturbing symptoms despite the medication, hyposensitization should be considered (Allergen-specific immunotherapy).

Perennial allergic conjunctivitis

• Mast cell stabilizer drops
  • Medication can be used as maintenance therapy for several months, as necessary.
• Short-term treatment with antihistamine drops, as necessary
• As prescribed by an ophthalmologist:
  • glucocorticoid drops in the beginning and for short-term use, as necessary
  • cyclosporine drops, as necessary

Atopic keratoconjunctivitis

• Avoidance of rubbing the eyes
• Cool compresses
• Frequent use of moisturizing drops
• Antihistamine drops, mast cell stabilizers (see above)
• Glucocorticoid or cyclosporine drops prescribed by an ophthalmologist

Vernal keratoconjunctivitis

• Avoidance of factors causing symptoms, such as wind, salt water, sunshine, rubbing the eyes
• Mast cell inhibitor + antihistamine combination drops (olopatadine x 2 or equivalent)
• Requires treatment and follow-up by an ophthalmologist
• Cyclosporine drops prescribed by an ophthalmologist may be considered; glucocorticoid drops prescribed by an ophthalmologist in the beginning of treatment and for short-term treatment during exacerbations, as necessary

Giant papillary conjunctivitis

• Elimination of mechanical irritation
  • A 2–4-week break in wearing contact lenses, careful cleaning of contact lenses, change of contact lens material or curvature and size
• Mast cell stabilizers
• Antihistamines
• Glucocorticoids prescribed by an ophthalmologist for severe inflammation
• Hyposensitization will not help as the condition is not due to environmental allergens but to mechanical irritation.

Non-allergic eosinophilic conjunctivitis

• Diagnosed disease requires treatment by an ophthalmologist.
• At first, glucocorticoid-antimicrobial eye drops, with the treatment monitored by an ophthalmologist
• Treatment is often continued for a long time using mast cell stabilizer and moisturizing eye drops.
• In addition, short courses of glucocorticoid drops are needed.
• In some cases, cyclosporine drops or tacrolimus products are needed.
• Long-term use of antihistamines should be avoided due to their drying effect.

• Acute allergic conjunctivitis can often be treated by a GP. If the symptoms are severe or last more than 3 weeks, examination by an ophthalmologist is indicated.
• Seasonal allergic conjunctivitis: refer to an ophthalmologist if there are disturbing symptoms despite medication.
• Perennial conjunctivitis: examination by an ophthalmologist recommended once or twice a year
• Refer the patient to an ophthalmologist if you suspect:
  • vernal keratoconjunctivitis
  • giant papillary conjunctivitis
  • non-allergic eosinophilic conjunctivitis

• Acute allergic conjunctivitis: follow-up by a GP or an ophthalmologist, as necessary
• Seasonal allergic conjunctivitis: follow-up once a year by a GP or an ophthalmologist, as necessary
• Perennial allergic conjunctivitis: follow-up by an ophthalmologist at least once a year
• Vernal keratoconjunctivitis (rare): in children, follow-up by an ophthalmologist at least 3 times a year
• Giant papillary conjunctivitis: follow-up by an ophthalmologist at least once a year
• Non-allergic eosinophilic conjunctivitis: follow-up by an ophthalmologist at least once a year