The London Itchy-Eye Survival Guide: Allergy vs Infection

If you live or work in London, you have probably experienced that familiar prickling, watering, itching sensation in your eyes — sometimes mild, sometimes distracting enough to ruin a working day. The question most people ask is simple: is this an allergy, or is it an infection? The answer matters, because allergic conjunctivitis and infective conjunctivitis look similar but have different causes, different management, and very different implications for the people around you. This guide helps you understand the key differences, what you can safely do at home, when to seek urgent help, and how an allergy blood test may help if your symptoms keep coming back.

Why Itchy Eyes Are So Common in London (Pollen + Pollution + Indoor Triggers)

London presents a unique combination of factors that make eye symptoms particularly common. Understanding these overlapping triggers helps explain why so many Londoners spend weeks each year reaching for eye drops.

• Pollen. London's parks, gardens, and tree-lined streets produce significant pollen loads from late February through to September. Tree pollen (particularly birch and plane tree) peaks in March–May, grass pollen dominates June–July, and weed pollen extends into early autumn. The London plane tree — one of the most common street trees in the capital — is a recognised allergen source (Allergy UK, 2025).
• Air pollution. London consistently records some of the highest nitrogen dioxide (NO₂) and particulate matter (PM2.5) levels in the UK. Air pollutants irritate the conjunctival surface directly and may also enhance the body's allergic response — making pollen-driven symptoms worse than they would be in cleaner air. Research suggests that the combination of pollen and pollution produces a greater inflammatory response than either alone (Royal College of Ophthalmologists, 2024).
• Indoor allergens. London's older housing stock, shared living spaces, and central heating systems create ideal conditions for dust mites, mould, and pet dander accumulation. For people sensitised to these allergens, eye symptoms can persist year-round — well beyond pollen season.
• Screen time and dry environments. Long hours in air-conditioned offices reduce blink rate and lower tear film quality, making the eye surface more vulnerable to both allergic and irritant triggers. This is a mechanical effect rather than an allergy, but it amplifies the discomfort.

The net result is that Londoners face a prolonged and overlapping set of triggers — outdoors and indoors — which is why hay fever itchy eyes in London can feel more persistent and harder to manage than in other parts of the country.

Allergic Conjunctivitis: The Classic Feature Set

Allergic conjunctivitis occurs when allergens — such as pollen, dust mite particles, mould spores, or pet dander — come into contact with the conjunctiva (the thin membrane covering the white of the eye and the inner eyelids). In a sensitised person, this triggers the release of histamine and other inflammatory mediators from mast cells in the eye tissue, producing the characteristic symptoms (Moorfields Eye Hospital, 2025).

Itch, Watering, Both Eyes, Seasonal Pattern

The hallmark features of allergic conjunctivitis include:

• Intense itch. This is the single most distinguishing symptom. Allergic conjunctivitis nearly always itches — often described as a deep, relentless, "can't stop rubbing" sensation. If your eyes are red but not itchy, an allergic cause is less likely.
• Watering. The eyes produce excess tears in response to the inflammatory irritation. The discharge in allergic conjunctivitis is typically watery and clear, not thick or coloured.
• Bilateral involvement. Both eyes are usually affected, often symmetrically — because both are exposed to the same airborne allergen. If only one eye is affected, other causes should be considered.
• Swollen eyelids. Mild to moderate puffiness around the eyes is common, particularly on waking or after rubbing.
• Seasonal or environmental pattern. Seasonal allergic conjunctivitis follows the pollen calendar — worsening in spring and summer, improving in winter. Perennial allergic conjunctivitis (triggered by indoor allergens) persists year-round but may fluctuate with indoor heating, humidity, or contact with pets.
• Associated nasal symptoms. Allergic conjunctivitis frequently accompanies hay fever — sneezing, nasal congestion, and a runny nose. The combination of eye and nasal symptoms (allergic rhinoconjunctivitis) is the most common presentation in pollen-sensitised individuals (NHS, 2025).

Infective Conjunctivitis: Typical Clues

Infective conjunctivitis — sometimes called "pink eye" — is caused by a virus or bacterium rather than an allergen. It is one of the most common eye infections in the UK and is usually self-limiting, but it can be uncomfortable and, in the case of bacterial infection, may benefit from treatment (NHS, 2025).

Sticky Discharge, Gritty Feeling, Contagious Patterns

The key features that help distinguish infective from allergic conjunctivitis include:

• Discharge. Viral conjunctivitis usually produces a watery discharge similar to allergic conjunctivitis, but bacterial conjunctivitis produces a thick, sticky, yellow-green discharge that may cause the eyelids to crust and stick together — particularly overnight. This "glued shut" sensation on waking is highly characteristic of bacterial infection.
• Gritty or burning sensation. Rather than the deep itch of allergic conjunctivitis, infective conjunctivitis typically produces a gritty, sandy, or burning feeling — as if something is in the eye.
• Often starts in one eye. Infective conjunctivitis commonly begins in one eye and may spread to the other within 24–48 hours. Allergic conjunctivitis usually affects both eyes from the outset.
• Contagious. Both viral and bacterial conjunctivitis can spread through direct contact, shared towels, or contaminated fingers. If other members of your household, school, or workplace develop symptoms around the same time, infection is the most likely cause.
• Associated cold symptoms. Viral conjunctivitis often accompanies or follows an upper respiratory tract infection (a cold). If your eye symptoms started during or shortly after a cold, a viral cause is probable.
• No seasonal pattern. Unlike allergic conjunctivitis, infective conjunctivitis can occur at any time of year and does not follow the pollen calendar.

A Simple Symptom Checker Table (Not a Diagnosis)

This table summarises the typical differences. It is intended as a general guide to help you describe your symptoms more accurately to a pharmacist, optometrist, or GP — not as a substitute for a clinical assessment.

Note: these are general patterns. Some people experience overlap (e.g., allergic conjunctivitis can occasionally become secondarily infected), and some viral infections can produce mild itch. If you are unsure, a pharmacist or optometrist can usually distinguish the two with a brief examination.

What You Can Do at Home Today (Safe Measures)

Many episodes of both allergic and mild infective conjunctivitis can be managed with straightforward measures. The following steps are generally safe for adults and are consistent with NHS and Moorfields guidance.

Cold Compress, Lubricating Drops, Avoid Rubbing, Hygiene

• Cold compress. A clean flannel soaked in cold water and placed over closed eyelids for 5–10 minutes can soothe itch and reduce puffiness. For allergic conjunctivitis, cold is particularly helpful because it constricts blood vessels and slows histamine release. Repeat as often as needed.
• Lubricating eye drops. Preservative-free artificial tears (available over the counter) help dilute allergens on the eye surface, wash away irritants, and restore the tear film. They are safe to use frequently and are compatible with most other eye treatments. In infective conjunctivitis, they can help flush discharge and ease the gritty sensation.
• Avoid rubbing. Rubbing provides momentary relief but causes further mast cell degranulation — releasing more histamine and worsening the itch cycle. It can also damage the corneal surface and, in infective conjunctivitis, spreads bacteria or virus from one eye to the other and onto your hands (Moorfields Eye Hospital, 2025).
• Hand and face hygiene. Wash your hands frequently, avoid touching your eyes, and use a separate towel for your face if you suspect infection. For allergic conjunctivitis, showering and changing clothes after outdoor exposure can help remove pollen from skin and hair.
• Antihistamine eye drops. Over-the-counter antihistamine drops (such as azelastine) can reduce itch and redness quickly by blocking histamine receptors on the eye surface.
• Mast cell stabiliser drops. Sodium cromoglicate is a mast cell stabiliser (not an antihistamine) available over the counter. It works best when used preventatively and regularly during allergy season rather than as a one-off rescue.
• Oral antihistamines. A non-drowsy oral antihistamine (cetirizine, loratadine, or fexofenadine) can help if eye symptoms are part of a broader allergic picture including nasal symptoms. They do not specifically target the eye, but reduce overall histamine levels (NHS, 2025).

Contact Lenses: When to Pause

Contact lens wear can complicate both allergic and infective conjunctivitis. General guidance includes:

• If you suspect infection — stop wearing contact lenses immediately and switch to glasses until symptoms have fully resolved. Wearing lenses over an infected eye increases the risk of a more serious corneal infection (keratitis).
• If symptoms are allergic — consider switching to daily disposable lenses during pollen season, as allergens can accumulate on reusable lens surfaces. Preservative-free lubricating drops can be used over daily disposables, but check compatibility with your lens type.
• If symptoms do not improve within a few days of removing lenses, see an optometrist to rule out contact lens–related keratitis or giant papillary conjunctivitis (a condition where the underside of the upper eyelid becomes inflamed in response to lens deposits).

If in doubt, your optometrist can advise on the safest lens-wearing strategy for your specific situation (Moorfields Eye Hospital, 2025).

When to Seek Urgent Eye Assessment

Most allergic and mild infective conjunctivitis resolves without complications. However, some symptoms require prompt assessment to rule out more serious eye conditions.

In London, urgent eye assessment is available through Moorfields Eye Hospital A&E (City Road, EC1), Western Eye Hospital (Marylebone Road, NW1), and most major hospital eye departments. Many high-street optometrists also offer emergency eye consultations and can refer onwards if needed (Moorfields Eye Hospital, 2025).

Where Allergy Testing Fits

If your itchy, watery eyes keep coming back — year after year during pollen season, or throughout the year regardless of season — allergy testing can help identify which specific allergens are driving your symptoms. This information is clinically useful because it allows more targeted avoidance strategies and helps your clinician decide whether allergen-specific treatments (such as immunotherapy) might be appropriate.

Linking Eye Symptoms to Hay Fever Triggers

Allergic conjunctivitis is driven by IgE-mediated sensitisation to specific allergens. A specific IgE blood test can measure IgE antibodies directed against individual allergens — such as timothy grass, birch pollen, house dust mite, or cat dander — and confirm which ones your immune system is responding to.

Knowing your specific triggers allows you to:

• Time your preventative treatment more precisely — for example, starting mast cell stabiliser drops two weeks before your specific pollen season begins
• Make targeted environmental changes — such as encasing bedding if dust mites are confirmed, or managing pet exposure if cat or dog dander is involved
• Provide your GP or allergy specialist with objective data to support a referral for immunotherapy, if appropriate
• Distinguish between hay fever eye symptoms and other causes of chronic eye irritation (such as dry eye syndrome or blepharitis)

An aeroallergen panel that covers UK-relevant pollens, mould spores, dust mites, and pet dander is usually the most informative starting point for recurrent allergic conjunctivitis.

Relevant London Aeroallergens to Consider

The following allergens are particularly relevant for London residents with recurrent eye symptoms:

• Timothy grass — the dominant grass pollen allergen in the UK, peaking June–July
• Common silver birch — a significant tree pollen allergen, peaking March–May
• London plane tree — not always included in standard panels but relevant in Central London where plane trees line many streets
• Mugwort — a weed pollen that peaks in late summer and is common in urban settings
• House dust mite (Dermatophagoides pteronyssinus and D. farinae) — the most common indoor allergen in the UK, causing year-round symptoms
• Cat dander (Fel d 1) — highly airborne and persistent in indoor environments
• Dog dander — less airborne than cat allergen but still a common sensitiser
• Alternaria and Cladosporium — mould spores that are airborne in damp conditions and during autumn months

Most of these allergens are included in a standard pollen identification blood test. If your diary suggests indoor triggers, adding dust mite and pet dander to the panel — or choosing a comprehensive aeroallergen profile — provides a fuller picture.

Testing is arranged through a simple nurse-led venous blood draw at our South Kensington clinic. You do not need to stop antihistamines beforehand — they do not affect IgE blood test results. Results are delivered to you securely and can be shared with your GP, optometrist, or allergy specialist for interpretation and guidance.

Frequently Asked Questions

Summary

Itchy, watery eyes are one of the most common complaints among Londoners — driven by a combination of seasonal pollen, urban air pollution, and indoor allergens. Allergic conjunctivitis is characterised by bilateral itch, clear watery discharge, and a seasonal or environmental pattern, while infective conjunctivitis tends to produce sticky discharge, grittiness, and contagious spread. Simple home measures — cold compresses, lubricating drops, avoiding rubbing, and good hygiene — can help manage mild episodes of either type.

If your eye symptoms recur predictably each season, persist year-round, or resist over-the-counter treatment, a targeted IgE blood test can help identify which specific allergens are responsible. This information supports more precise avoidance strategies, better-timed preventative treatment, and — when shared with your clinician — may help determine whether immunotherapy or specialist referral is appropriate.

Sources

• NHS — Conjunctivitis overview, symptoms, causes, and treatment (2025): nhs.uk/conditions/conjunctivitis
• NHS — Allergic conjunctivitis and hay fever guidance (2025): nhs.uk/conditions/allergic-conjunctivitis
• Moorfields Eye Hospital — Allergic eye disease, infective conjunctivitis, and emergency eye assessment guidance (2025): moorfields.nhs.uk
• Allergy UK — Allergic conjunctivitis factsheet, pollen and indoor allergen guidance (2025): allergyuk.org
• Royal College of Ophthalmologists — Air pollution and ocular surface disease position statement (2024): rcophth.ac.uk
• BSACI — Guidelines on the management of allergic rhinitis and conjunctivitis (2024): bsaci.org
• NICE — Clinical Knowledge Summary: conjunctivitis — allergic and infective, updated 2024: nice.org.uk
• Met Office / University of Worcester — UK pollen calendar and London-specific aeroallergen data (2025): metoffice.gov.uk/weather/warnings-and-advice/seasonal-advice/pollen