Latanoprost Side Effects: What to Expect and When to Call Your Doctor

Latanoprost (brand name Xalatan) is generally well tolerated, but like any medication, it can cause side effects. Most are mild and eye-related. Some are permanent. A few are rare but serious. Knowing what to expect helps you stay safe and avoid unnecessary anxiety — or unnecessary delay in seeking care when it's needed.

Common Side Effects of Latanoprost (Affecting 5–15% of Patients)

These side effects are well-documented and expected with prostaglandin analogue use. They are not reasons to stop the medication without speaking to your doctor:

Conjunctival hyperemia (eye redness). The most common side effect, occurring in 5–15% of patients. The whites of the eyes may appear pink or red. This is usually mild and often improves with continued use.

Foreign body sensation. A feeling that something is in your eye — gritty, scratchy, or sandy sensation. Usually temporary and mild.

Burning and stinging. Brief stinging or burning immediately after instilling the drop. This usually passes within 30–60 seconds.

Blurred vision. Temporary blurring immediately after using the drop. Do not drive or operate machinery until your vision clears.

Itching. Mild eye itching is common. If severe or accompanied by swelling, contact your doctor to rule out an allergic reaction.

Unique and Potentially Permanent Side Effects

Latanoprost has several distinctive side effects that set it apart from other drug classes:

Iris darkening (heterochromia). Latanoprost may cause the iris (colored part of your eye) to gradually become more brown. This occurs more commonly in people with mixed-color irises (blue-brown, green-brown, hazel). The change develops over months to years and may be permanent, even if you stop the medication. This is a cosmetic change only — it does not affect vision or IOP control.

Eyelash changes. Eyelashes in the treated eye may become longer, thicker, darker, and more numerous. These changes typically reverse after stopping the medication.

Eyelid skin darkening. The skin around the treated eye may become darker. This typically reverses after stopping the medication.

Important: If you use latanoprost in only one eye, these cosmetic changes will affect only that eye — creating an asymmetric appearance. Inform your doctor if this is a concern.

Less Common Side Effects (1–4% of Patients)

Dry eyes or excessive tearing

Eye pain or discomfort

Eyelid crusting, swelling, or redness

Sensitivity to light (photophobia)

Cold or upper respiratory symptoms (4% — may be coincidental)

Serious Side Effects: When to Call Your Doctor Immediately

These are rare but require prompt medical attention:

Macular edema. Swelling in the central retina that can affect vision. Risk is higher in aphakic patients or those with a damaged posterior lens capsule. Report any sudden vision changes immediately.

Reactivation of herpetic keratitis. If you have a history of herpes simplex eye disease, tell your eye doctor before starting latanoprost. It may reactivate this condition.

Severe allergic reaction. Signs include severe eye swelling, facial swelling, difficulty breathing, or hives. Seek emergency care if these occur.

Uveitis or iritis. Rare eye inflammation. Symptoms include deep eye pain, light sensitivity, and red eye. Contact your eye doctor promptly.

Tips to Minimize Side Effects

Apply the drop at night (as directed) — this minimizes cosmetic awareness of redness during the day

After instilling the drop, gently press the inner corner of your eye (nasolacrimal duct occlusion) for 1 minute to reduce systemic absorption

Blot excess drops from your eyelid with a tissue to reduce pigmentation around the eye

Remove contact lenses before instilling; wait 15 minutes before reinserting

See also: Latanoprost drug interactions | What is latanoprost?