Is It Allergy or Dry Eye?

How to discern between the two conditions when symptoms can overlap

When my kids were little, they had trouble distinguishing between the words “itch” and “scratch,” so they often used them interchangeably. Although these words have some relationship, it’s incorrect to mistake one for the other. Similarly, dry eye disease (DED) and ocular allergy have some relationship to one another, muddying the diagnostic waters, yet they are different conditions. In fact, a study published in the Annals of Allergy, Asthma and Immunology reveals a clinically significant overlap between the symptoms of dryness (45.3%) and itch (57.7%). So, how can optometrists tell ocular allergy and DED apart and best manage either patient?


  • Case history. The patient’s account of his symptoms is the first step to making the correct assessment. If the patient reports “itch,” typically a tell-tale sign of allergy, optometrists must still ask, “where does it itch?” as itch can be a symptom of DED as well (see in the above-mentioned study).
    With allergy, for example, the itch tends to emanate from the bulbar and tarsal conjunctiva.
    In the case of DED, the itch tends to be localized to the lid margin, with demodex or blepharitis as potential causes.
    Other items to note from the case history include the current use of ocular dryness-causing medications, such as antidepressants, and systemic manifestations of allergy, such as rhinitis.
  • Diagnostic evaluation. Testing works to confirm or refute your suspicions based on the case history.
    Bulbar conjunctivochalasis, edema, hyperemia, infiltrates and papillae are seen with ocular allergy. Additionally, optometrists may note an edematous puncta, which can contribute to poor drainage and lead to a complaint of epiphora, mimicking DED.

Papillae in allergic conjunctivitis.

Many states allow optometrists to perform in-office allergy skin testing to determine which allergen(s) are causing the patient’s issues. Once the specific offenders are identified, the patient can be better prepared to both avoid (if possible) and treat them. If, however, your state doesn’t permit allergy testing or you don’t have it available in your office, consider developing a relationship with an allergist to facilitate a smooth referral from your practice.

Poor lid hygiene, ocular surface staining in the nasal bulbar conjunctiva or cornea, absence of papillae from the tarsal conjunctiva and a decreased lacrimal lake are clinical signs of DED.


Treating ocular allergy can have the cascade effect of causing DED: Anti-histamines and decongestants used to treat allergy are known to increase ocular dryness.

Often, allergy may present as an acute condition, causing only a short-term increase in ocular dryness. But if your patient suffers from chronic allergies, a long-term game plan will need to be created to avoid a negative impact to both his quality of life and ocular surface. In such cases, optometrists may initiate DED therapies to offset the allergy medication-caused symptoms successfully.

As open dialogue with the patient can properly align expectations and set them up for success, optometrists should educate these patients about the potential side effects of treatment. Doing so is essential to helping them manage an uptick in symptoms they may experience. OM