In short: Seasonal allergies flare at predictable times of year and are usually caused by tree, grass or weed pollen. Year-round (perennial) allergies are more often caused by house dust mite, pets or mould, and some year-round nasal symptoms are not allergic at all. Allergy testing, either a skin prick test or a blood test for specific IgE, can help pin down the trigger, but results only make sense when they are read alongside your symptoms.

This guide, written by a Ready Health prescribing pharmacist, explains how to tell seasonal and year-round allergies apart and what allergy testing can and cannot tell you.

What is the difference between seasonal and year-round allergies?

	Seasonal allergies	Year-round allergies
Typical triggers	Tree pollen (spring), grass pollen (early summer), weed pollen (late summer)	House dust mite, cats, dogs and other animals, indoor mould, some workplace substances
Pattern	Comes and goes with the pollen season; worse outdoors and on dry, windy days	Present most of the year; often worse indoors, at night or first thing in the morning
Common symptoms	Sneezing, runny nose, itchy and watery eyes	Blocked nose, catarrh, mouth breathing, poor sleep; eye symptoms may be milder

Many people have both, for example a dust mite allergy that is present all year and gets worse when grass pollen arrives.

Could my symptoms be something other than allergy?

Yes. Non-allergic rhinitis can cause a runny or blocked nose triggered by smoke, perfume, temperature changes or alcohol. Overuse of decongestant sprays, some medicines, hormonal changes such as pregnancy, and structural problems such as nasal polyps can also produce similar symptoms. This is one reason why a clinical history matters before any test is ordered.

How is an allergy diagnosed?

Diagnosis starts with a careful history: what symptoms you have, when and where they happen, and what makes them better or worse. Testing is then used to confirm or rule out specific triggers. The validated tests are:

Skin prick test: a drop of allergen extract is placed on the forearm and the skin is gently pricked. A raised, itchy bump after around 15 minutes suggests sensitisation. Antihistamines need to be stopped for a period beforehand, so follow the instructions you are given.
Specific IgE blood test: measures antibodies to particular allergens. It is useful when skin testing is not suitable, for example with widespread eczema or if antihistamines cannot be stopped.

Patch testing is a different test used for contact allergy of the skin, not hay fever.

What do allergy test results actually mean?

A positive result shows that your immune system is sensitised to an allergen. It does not prove that the allergen is causing your symptoms: many people have positive tests to things that never bother them. Equally, a negative result alongside a convincing history needs careful interpretation. That is why results should always be explained by a clinician who knows your history.

Tests marketed directly to the public, such as hair analysis, applied kinesiology, Vega testing and IgG "intolerance" panels, have no reliable evidence for diagnosing allergy and can lead to unnecessary changes to diet or lifestyle.

How does knowing the trigger help?

Timing treatment: if you know you react to grass pollen, you can start a steroid nasal spray a couple of weeks before that season.
Targeted avoidance: reducing exposure to pets or indoor damp makes more sense once the trigger is confirmed.
Specialist treatment: immunotherapy for severe allergy is only considered once the trigger is confirmed by testing.

Treatment itself is similar for most allergic rhinitis: non-drowsy antihistamines, a regular steroid nasal spray and eye drops, adjusted by a clinician if symptoms persist.

Frequently asked questions

Can you develop allergies as an adult?

Yes. Allergies, including hay fever, can start at any age, and symptoms can change over time.

Is a blood test or skin prick test better?

Both are validated. The choice depends on your skin, medicines, the allergens being tested and the clinical setting.

Can testing tell me if my symptoms will get worse?

Not reliably. Test results do not predict how severe future symptoms will be.

Should I stop my antihistamines before an allergy test?

For a skin prick test, usually yes, for a set number of days. For a blood test, usually not. Always follow the instructions from the clinic doing the test.

Key takeaways

Seasonal allergies follow the pollen calendar; year-round symptoms point to indoor triggers or non-allergic causes.
Diagnosis starts with your history, and testing is used to confirm it.
Skin prick and specific IgE blood tests are validated; hair, kinesiology, Vega and IgG tests are not.
A positive test shows sensitisation, not necessarily the cause of your symptoms.

Sources and further reading

Last reviewed: October 2026 by Shamir Patel, Independent Prescribing Pharmacist, Ready Health. This article is general information and does not replace advice from your own clinician.

If you are unsure what is behind your symptoms, Ready Health in Standish, Wigan, offers allergy consultations and testing, with results explained by a clinician.

Seasonal or Year-Round Allergies? How Allergy Testing Can Help