Allergic conjunctivitis


  • 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.

Symptoms and findings

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

Differential diagnosis


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.

Criteria for referral

  • 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
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