Allergy Eye Drops

Concise summaries of common allergy eye drops and medications used in optometric practice in Singapore, including practical guidance on pharmacology, dosing, patient selection, and monitoring.

Last updated: March 2026

What are allergy eye drops?

Allergy eye drops (topical ocular antiallergic agents) are pharmaceutical preparations applied directly to the ocular surface to manage allergic conjunctivitis — the most common allergic eye disease in clinical practice. They act on the IgE-mediated hypersensitivity cascade triggered by environmental allergens such as house dust mites, pet dander, mould spores, and pollen.

In Singapore, the dominant allergens are perennial: house dust mite (Dermatophagoides pteronyssinus and D. farinae) due to the tropical, humid climate. Seasonal variation is less pronounced than in temperate countries, meaning year-round management is often required.^[1,3]

Drug classes

Dual-action agents (antihistamine + mast cell stabilizer) — current first-line choice; combine rapid H1 blockade with mast cell stabilization for both acute relief and prophylaxis (e.g., olopatadine, ketotifen).
Mast cell stabilizers — prevent degranulation and mediator release; purely prophylactic and require consistent daily use before allergen exposure (e.g., sodium cromoglicate, lodoxamide).
Corticosteroids — potent anti-inflammatory for severe or refractory cases; restricted to short-term use with mandatory IOP monitoring (e.g., fluorometholone, loteprednol, prednisolone).

Who are they for?

Allergy eye drops are indicated for patients presenting with allergic conjunctivitis. In Singapore, allergic conjunctivitis is highly prevalent given the year-round high humidity and perennial house dust mite burden. Andiappan et al. found that over 80% of allergic individuals in Singapore were sensitised to house dust mites, with mono-specific sensitisation being the dominant pattern — unlike temperate populations with multi-allergen sensitisation.^[2]

Patient profiles

Seasonal / perennial allergic conjunctivitis

Most common; bilateral itch, watering, papillae. House dust mite dominant in SG.

Vernal keratoconjunctivitis (VKC)

Severe, recurrent in young males; giant papillae, shield ulcers. Mast cell stabilizers (lodoxamide) are key.

Atopic keratoconjunctivitis (AKC)

Adults with atopic dermatitis; chronic, potentially sight-threatening. Multi-modal management needed.

Contact lens-related allergy (CLPC)

Papillary reaction to lens deposits; cease wear, treat with mast cell stabilizer or dual-action agent.

Caution — contact lens wearers

Most allergy drops contain benzalkonium chloride (BAK) as preservative, which adsorbs onto soft contact lenses and causes toxic keratopathy. Advise patients to instil drops at least 15 minutes before lens insertion, or use preservative-free formulations where available.

When should they be prescribed?

Acute symptomatic relief

Start a dual-action antihistamine/mast cell stabilizer (e.g., olopatadine or ketotifen) at the first presentation of itch, watering, and redness. Onset is rapid — most agents provide relief within 3–15 minutes.

Prophylactic / maintenance use

Pure mast cell stabilizers (sodium cromoglicate/Allergocrom, lodoxamide/Alomide) must be used continuously and consistently — begin 2–4 weeks before anticipated allergen exposure. In Singapore where dust mite exposure is year-round, ongoing daily dosing is typically required.

Escalation to steroids

Reserve topical corticosteroids for acute severe flares or VKC/AKC unresponsive to first-line agents. Loteprednol (0.5%) is preferred over prednisolone for its lower IOP-raising risk. Duration should be as short as clinically possible with IOP checks at 2–4 weeks. Co-prescribing with a corneal specialist is advisable for VKC or AKC.

Severity	Recommended agent	Duration
Mild — intermittent	Ketotifen or olopatadine PRN	As needed
Mild-moderate — persistent	Olopatadine OD/BD daily	Ongoing season / year-round
Moderate — VKC	Lodoxamide QID + olopatadine BD	≥3 months; then step-down
Severe — AKC / refractory	Short-course loteprednol + dual agent	2–4 weeks; specialist co-manage

Where are they available in Singapore?

In Singapore, allergy eye drops are regulated by the Health Sciences Authority (HSA) under the Medicines Act. Availability and legal supply status varies by agent:

Scope of practice — Singapore optometrists

Under the Optometrists and Opticians Act (Cap. 213A), Singapore-registered optometrists are authorised to examine eyes, assess visual function, and prescribe optical appliances (spectacles and contact lenses). They do not have the authority to prescribe, supply, or administer therapeutic medications, including prescription allergy eye drops. Any patient requiring POM treatment must be referred to a medical doctor — typically an ophthalmologist or a GP with ophthalmic experience.^[4,5]

General Sale (OTC): Ketotifen 0.025% (Zaditen) is classified as a general sale medicine in Singapore and can be purchased directly without prescription at major pharmacy chains including Guardian, Watsons, and Unity.
Pharmacy medicine (P): Sodium cromoglicate 2% (Allergocrom) is a Pharmacy-only medicine — available without prescription but only from a licensed retail pharmacy under pharmacist supervision.
Prescription-only (POM): Olopatadine (Patanol, Pataday), lodoxamide (Alomide), and all topical corticosteroids including fluorometholone (FML), prednisolone (Pred Forte), and loteprednol (Lotemax) require a prescription from a registered medical practitioner. Optometrists detecting allergic conjunctivitis warranting POM treatment must refer to a doctor.
Public hospitals: SNEC, NUH Eye Institute, and TTSH outpatient formularies include olopatadine, lodoxamide, and loteprednol — prescribed by ophthalmologists and dispensed in-house or via linked pharmacies.
HSA product verification: Current registration status and supply schedule for all products can be confirmed via the HSA product registration portal (hsa.gov.sg). Always verify before recommending or referring for any specific product.^[4]

Why use topical agents over oral antihistamines?

Topical ocular antiallergic agents deliver high local drug concentrations directly to the conjunctival mast cells and H1 receptors with minimal systemic absorption, producing faster onset and fewer systemic adverse effects compared with oral antihistamines.

Faster onset

Relief within 3–15 minutes vs. 30–60 minutes for oral agents.

Lower systemic load

Reduced drowsiness, dry mouth, urinary retention — relevant for elderly patients and drivers.

Targeted delivery

High local drug concentrations at the ocular surface without systemic peak levels.

Additive benefit

Topical drops and oral antihistamines can be combined for severe systemic atopy with ocular involvement.

Oral antihistamines (e.g., cetirizine, loratadine) may be appropriate when nasal or dermatological allergy coexists, or when the patient cannot tolerate eye drops. In such cases, combination with a topical mast cell stabilizer or dual-action agent is often more effective than oral therapy alone.^[6]

How to use allergy eye drops — patient instructions

Instillation technique

Wash hands thoroughly before handling the bottle.
Tilt head back slightly and gently pull down the lower eyelid to form a pocket.
Hold the bottle inverted and squeeze one drop into the lower fornix — avoid touching the tip to the eye or eyelids.
Gently close the eye and apply nasolacrimal occlusion (finger to inner corner) for 1–2 minutes to reduce systemic absorption.
If using more than one drop type, wait at least 5 minutes between each preparation.
Recap the bottle immediately after use; store as directed (most at room temperature, away from heat/light).

Contact lens guidance

Remove soft contact lenses before instilling drops. Reinsert after 15 minutes if using BAK-preserved formulations.
Rigid gas-permeable (RGP) wearers: instil drops, wait 15 minutes, then insert lenses.
During acute allergic flares, cease lens wear until symptoms resolve and conjunctiva is quiescent.

Monitoring recommendations

All patients: Review at 4–6 weeks to assess symptom control and compliance.
Steroid users: IOP check at 2 weeks and 4 weeks. Discontinue if IOP rises >5 mmHg above baseline or exceeds 21 mmHg.
VKC patients: Corneal staining and anterior segment review each visit; monitor for shield ulcer formation.
Children: Engage parents on correct instillation; lodoxamide is approved from age 2 years; olopatadine from age 3.

Common allergy eye drops in Singapore

All agents listed are, or have been, registered with HSA Singapore or are available through registered importers. Verify current product registration at hsa.gov.sg before prescribing.

Brand (Generic)	Mechanism	Dosing	Min. Age	Side Effects	Clinical Notes
Patanol Olopatadine 0.1% POM	Dual: H1-antihistamine + mast cell stabilizer	1 drop BD	≥3 years	Mild stinging, headache, dry eye	First-line for seasonal & perennial allergic conjunctivitis; well-tolerated for long-term use
Pataday Olopatadine 0.2% POM	Dual: H1-antihistamine + mast cell stabilizer	1 drop OD	≥3 years	Mild stinging, headache, dry eye	Once-daily convenience; same mechanism as Patanol at higher concentration
Zaditen Ketotifen 0.025% OTC	Dual: H1-antihistamine + mast cell stabilizer	1 drop BD, 8–12 hours apart	≥3 years	Burning/stinging, conjunctival injection	OTC availability in Singapore; rapid symptom relief; onset within minutes
Alomide Lodoxamide 0.1% POM	Mast cell stabilizer	1–2 drops QID for up to 3 months	≥2 years	Transient burning, stinging, blurred vision	Superior to cromolyn for vernal keratoconjunctivitis; requires consistent use for prophylaxis
Allergocrom Sodium Cromoglicate 2% P	Mast cell stabilizer — inhibits mast cell degranulation, preventing release of histamine and inflammatory mediators	1 drop QID at regular intervals	≥4 years	Transient stinging/burning on instillation, foreign body sensation	Purely prophylactic; not a rescue agent — requires consistent regular use for effect; discard 4 weeks after opening; soft contact lenses must not be worn during treatment
FML Fluorometholone 0.1% POM	Corticosteroid (anti-inflammatory)	1 drop BD–QID; taper as required	≥2 years (with supervision)	Raised IOP, cataract, secondary infection	Short-term only for severe acute flares; IOP monitoring mandatory
Pred Forte Prednisolone 1% POM	Corticosteroid (anti-inflammatory)	1 drop 2–4× daily; taper as required	≥2 years (with supervision)	Raised IOP, cataract, secondary infection	Higher potency steroid; reserve for severe inflammation; mandatory IOP monitoring
Lotemax Loteprednol 0.5% POM	Retrometabolic corticosteroid	1–2 drops QID; taper over 2–4 weeks	≥18 years	Lower IOP-raising risk vs. prednisolone; mild stinging	Preferred steroid for allergic conjunctivitis when steroid is indicated; safer IOP profile
Naphcon-A Naphazoline 0.025% + Pheniramine 0.3% OTC	Decongestant (α-adrenergic vasoconstrictor) + H1-antihistamine	1–2 drops up to 4× daily; not for continuous use beyond 72 hours	≥6 years	Rebound hyperaemia, mydriasis, raised IOP, systemic absorption risk	Available OTC at pharmacies; short-term symptomatic relief only — not for chronic use; contraindicated in narrow-angle glaucoma; avoid in contact lens wearers; rebound redness common with prolonged use
Optizoline Tetrahydrozoline 0.05% OTC	Decongestant (α-adrenergic vasoconstrictor)	1–2 drops up to 4× daily; not for continuous use beyond 72 hours	≥6 years	Rebound hyperaemia, pupil dilation, raised IOP	Available OTC; for temporary redness relief only — not a true allergy treatment; high rebound redness risk with frequent use; contraindicated in narrow-angle glaucoma; avoid in contact lens wearers
Relestat Epinastine 0.05% POM	Dual: H1-antihistamine + mast cell stabilizer	1 drop BD	≥3 years	Mild burning/stinging, follicular conjunctivitis, dry eye	Comparable efficacy to olopatadine; does not penetrate the blood-brain barrier — reduced sedation risk; contact lenses should be removed 15 minutes before instillation

Legend

POMPrescription Only Medicine — Sold or supplied to the public on prescription only.

PPharmacy Medicine — Sold or supplied from any licensed retail pharmacy under pharmacist supervision.

OTCGeneral Sales List (GSL) — Sold or supplied to the public without restriction.

Dosing reflects standard adult doses unless noted. Always refer to the approved product insert for full prescribing information. BD = twice daily, QID = four times daily, OD = once daily, PRN = as needed.

References

[1] Chew FT, Zhang L, Ho TM, Lee BW. House dust mite fauna of tropical Singapore. Clin Exp Allergy. 1999;29(2):201–206. PMID: 10051724.
[2] Andiappan AK, Puan KJ, Lee B, et al. Allergic airway diseases in a tropical urban environment are driven by dominant mono-specific sensitisation against house dust mites. Allergy. 2014;69(4):501–509. PMID: 24456108.
[3] Thong BYH. Allergic conjunctivitis in Asia. Asia Pac Allergy. 2017;7(2):57–64. PMID: 28487836. PMC: PMC5410412.
[4] Republic of Singapore. Optometrists and Opticians Act 2007 (No. 16 of 2007). Singapore Statutes Online. Available at: sso.agc.gov.sg/Act/OOA2007 (accessed March 2026).
[5] George PP, Chng OSY, Siow K, et al. Is there scope for expanding the optometrist's scope of practice in Singapore? A survey of optometrists and opticians. Cont Lens Anterior Eye. 2019;42(3):258–264. PMID: 30819628.
[6] Katelaris CH. Ocular allergy in the Asia Pacific region. Asia Pac Allergy. 2011;1(3):108–114. PMID: 22053306. PMC: PMC3206247.
[7] Kam KW, Chen LJ, Wat N, Young AL. Topical olopatadine in the treatment of allergic conjunctivitis: a systematic review and meta-analysis. Ocul Immunol Inflamm. 2017;25(5):663–677. PMID: 27192186.
[8] Abelson MB, Spitalny L. Combined analysis of two studies using the conjunctival allergen challenge model to evaluate olopatadine hydrochloride. Am J Ophthalmol. 1998;125(6):797–804. PMID: 9645717.
[9] Bartlett JD, Horwitz B, Laibovitz R, Howes JF. Intraocular pressure response to loteprednol etabonate in known steroid responders. J Ocul Pharmacol. 1993;9(2):157–165. PMID: 8345288.
[10] Comstock TL, DeCory HH. Advances in corticosteroid therapy for ocular inflammation: loteprednol etabonate. Int J Inflamm. 2012;2012:789623. PMID: 22536546. PMC: PMC3321285.

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