Allergic Conjunctivitis Differential Diagnoses

Updated: Jul 07, 2022
  • Author: Mark Ventocilla, OD, FAAO; Chief Editor: Andrew A Dahl, MD, FACS  more...
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Diagnostic Considerations

Allergic conjunctivitis must be differentiated from viral and bacterial conjunctivitis or other infectious external diseases of the eye. Clinical features (eg, recent exposure to an individual with infective conjunctivitis) may be helpful in this regard.

The main distinction between seasonal and perennial allergic conjunctivitis, as implied by the names, is the timing of symptoms (see Pathophysiology). Major differentiating factors between vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC) are shown in the table below.

Table. Major Differentiating Factors Between VKC and AKC (Open Table in a new window)




Age at onset

Generally presents at a younger age than AKC' first decade

Second to third decade


Males are affected preferentially.

No sex predilection

Seasonal variation

Typically occurs during spring months

Generally perennial


Thick mucoid discharge

Watery and clear discharge

Conjunctival scarring

Moderate incidence of conjunctival scarring

Higher incidence of conjunctival scarring

Horner-Trantas dots

Horner-Trantas dots and shield ulcers are commonly seen.

Presence of Horner-Trantas dots is rare.

Corneal neovascularization

Not present, unless secondary to infectious keratitis

Deep corneal neovascularization tends to develop

Presence of eosinophils in conjunctival scraping

Conjunctival scraping reveals eosinophils to a greater degree in VKC than in AKC

Presence of eosinophils is less likely

Differential Diagnoses