Sneezing through every summer? You might be a candidate for one of the most effective allergy treatments available today.
Quick Answer
A hayfever injection — most commonly a corticosteroid shot called Kenalog — provides fast, season-long relief from hay fever symptoms. It is typically administered once per allergy season by a healthcare professional and works by suppressing the overactive immune response triggered by pollen.
If you’ve tried antihistamines, nasal sprays, and eye drops and still spend every spring and summer in a fog of sneezing, watery eyes, and constant congestion, you’re not alone. Hay fever affects an estimated one in five people in the UK — and for many, over-the-counter remedies simply don’t cut it.
That’s where the hayfever injection comes in. In recent years it has become one of the most talked-about treatments among allergy sufferers, offering the promise of relief that lasts the entire pollen season rather than just a few hours at a time. But is it right for everyone? What are the risks? And where can you actually get one?
This guide covers everything you need to know — plainly, honestly, and without the jargon.
1 in 5
people in the UK affected by hay fever
~80%
report significant symptom relief after a corticosteroid injection
4–6 wks
typical duration of effect per injection
What Exactly Is a Hayfever Injection?
When most people talk about a hayfever injection, they are usually referring to a corticosteroid injection — most commonly triamcinolone acetonide, sold under the brand name Kenalog. It’s a long-acting steroid that is injected intramuscularly (usually into the buttock) and slowly releases over several weeks, providing a sustained anti-inflammatory effect throughout the pollen season.
The drug dampens the immune system’s overreaction to allergens like grass, tree, and weed pollen. In practical terms, this means reduced sneezing, less nasal congestion, fewer itchy eyes, and — for many people — the ability to actually enjoy the outdoors again.
It’s worth distinguishing this from allergen immunotherapy injections (also called allergy desensitisation or SCIT), which is a separate, longer-term treatment that involves a course of injections over months or years to gradually retrain the immune system. Both are types of allergy injection, but they work very differently and have different goals.
Important distinction
A hayfever injection (Kenalog) is a one-off corticosteroid shot for seasonal relief. Allergen immunotherapy is a multi-year treatment programme aimed at permanent desensitisation. Always confirm which one is being discussed with your clinician.
How the Hayfever Injection Works
Hay fever is, at its core, an immune overreaction. When pollen enters your nasal passages, your immune system mistakenly identifies it as a threat and triggers a cascade of inflammatory responses — releasing histamine, causing blood vessels to dilate, and producing all the familiar miserable symptoms.
Corticosteroids like triamcinolone are powerful anti-inflammatory agents. Administered by injection rather than as a daily pill or spray, the drug bypasses the digestive system and delivers a steady, controlled dose of the steroid directly into the bloodstream over several weeks.
This means you don’t have to remember to take a tablet every morning. The effect is consistent, which can make a significant practical difference — particularly for people whose work, sport, or daily life is heavily disrupted during allergy season.
Who Is a Good Candidate for This Treatment?
The hayfever injection is generally considered for people whose symptoms are severe, persistent, and not adequately controlled by standard treatments. Clinicians typically assess candidacy based on:
- Failure or inadequate response to antihistamines, nasal steroids, and/or eye drops
- Symptoms that significantly impair daily functioning, sleep quality, or work performance
- An allergy season that is particularly intense or long-lasting for the individual
- No contraindications such as uncontrolled diabetes, active infections, osteoporosis, or certain pregnancy-related concerns
It’s important to have a proper consultation before receiving the injection. A qualified clinician will review your medical history, current medications, and the severity of your symptoms to determine whether the risks and benefits are appropriate for your situation.
What Are the Risks and Side Effects?
No treatment is without risk, and the hayfever injection is no exception. Because corticosteroids suppress immune function and affect metabolic processes, there are several side effects to be aware of.
Common and generally mild
- Temporary skin thinning or fat loss at the injection site
- Short-term increase in blood sugar levels (particularly relevant for people with diabetes)
- Mild mood changes or difficulty sleeping immediately after injection
- Weight gain with repeated use
Less common but more serious
- Suppression of the adrenal gland’s own cortisol production (with frequent use)
- Impact on bone density over time — this is why the injection should not be given more than once per year and is not recommended as a long-term recurring treatment
- Rare risk of avascular necrosis (interruption of blood supply to joints) with high doses or repeated administration
A note on NHS availability
In the UK, the hayfever injection (Kenalog) is not routinely available on the NHS for hay fever. This is largely because NHS guidelines favour treatments with fewer systemic side effects, such as intranasal corticosteroid sprays. Most people seeking this injection do so privately, through a GP or a private allergy clinic.
Getting a Hayfever Injection in London
If you’re based in the capital and looking for a hayfever injection in London, there is no shortage of options — from private GP clinics and allergy specialists to dedicated travel health and minor procedures services.
Getting a hayfever injection in London typically involves a brief consultation (in-person or sometimes via video call), a review of your medical history, and the injection itself, which takes only a few minutes. The whole appointment is often completed within 30 minutes. Costs vary by provider but typically range from £50 to £150, depending on the clinic and whether a consultation fee is included separately.
When choosing a provider, look for clinics staffed by fully registered medical professionals (GPs or nurse prescribers with prescribing authority). The injection should always be administered in a clinical setting with appropriate facilities in case of adverse reactions.
What to ask before booking
- Is a medical consultation included, or is there a separate fee?
- What is the clinician’s qualification and experience with this procedure?
- How does the clinic handle adverse reactions?
- Are there any circumstances under which they would decline to administer the injection?
How Does It Compare to Other Hay Fever Treatments?
Understanding where the hayfever injection sits in the broader landscape of allergy treatment helps you make a more informed decision.
Antihistamines (cetirizine, loratadine, fexofenadine) remain the first-line treatment for most people. They’re cheap, widely available, and carry a very low risk profile. The main limitation is that they need to be taken daily, they work better at preventing than treating active symptoms, and in some people, they cause fatigue or simply aren’t effective enough.
Intranasal corticosteroid sprays (like Flonase or Nasonex) are highly effective and specifically recommended in clinical guidelines for moderate-to-severe hay fever. They require consistent daily use and take up to two weeks to reach their full effect — so they work best when started before the pollen season begins.
Sublingual immunotherapy (SLIT) involves daily drops or tablets placed under the tongue over several years. It can produce lasting reductions in sensitivity. It’s more of a long-term investment but is increasingly available and has fewer systemic risks than injection-based corticosteroids.
Allergen immunotherapy injections (SCIT) are the gold standard for allergy desensitisation and can produce long-term or even permanent relief. They’re conducted in specialist allergy centres over a period of three to five years and are not suitable for everyone.
The hayfever injection (corticosteroid) is best thought of as a rapid, season-saving intervention for people who need fast relief and whose symptoms are severe — not as a long-term strategy in isolation.
Frequently Asked Questions
How quickly does the hayfever injection work?
Most people notice improvement within 24 to 72 hours of receiving the injection. For some, relief is felt even sooner. The effect typically lasts between four and eight weeks, depending on the individual and the severity of the pollen season.
Can I have the injection every year?
Most clinicians recommend limiting corticosteroid injections to once per allergy season and no more than once per year. Repeated annual use increases the risk of longer-term systemic side effects, particularly on bone density and adrenal function. Some people use it for a season or two while transitioning to a longer-term strategy like immunotherapy.
Is the hayfever injection the same as an allergy shot?
Not quite. “Allergy shots” usually refers to allergen immunotherapy (SCIT), which involves repeated injections of small amounts of the allergen to gradually desensitise the immune system. The hayfever injection (Kenalog) is a corticosteroid that suppresses symptoms but does not address the underlying sensitivity.
Is it safe if I have diabetes?
Corticosteroids can raise blood sugar levels significantly, sometimes for one to two weeks after the injection. If you have diabetes — type 1 or type 2 — this injection carries additional risks and you should discuss it carefully with both your GP and your diabetologist before proceeding.
Can children have the hayfever injection?
Kenalog is generally not recommended for children with hay fever. The side effect profile, including effects on growth and bone density, makes it a poor risk-benefit trade-off for paediatric patients. Allergy specialists can advise on age-appropriate alternatives.
The Bottom Line
The hayfever injection is a legitimate and effective short-term treatment for people with severe hay fever who haven’t found adequate relief from standard therapies. For the right patient, it can genuinely transform the experience of spring and summer — from weeks of misery to seasons that are actually enjoyable.
That said, it’s not a treatment to take lightly. The systemic nature of corticosteroids means there are real risks, especially with repeated use. It should always be administered by a qualified clinician following a proper consultation — not as a walk-in procedure with minimal oversight.
If you’re considering a hayfever injection, start by speaking with your GP or a private allergy specialist. They can help you weigh the options, confirm whether you’re a suitable candidate, and make sure you’re using the injection as part of a broader, sustainable hay fever management plan — not just as a quick fix year after year.
Because the best treatment isn’t always the most dramatic one. It’s the one that fits your life, your health, and your long-term wellbeing.
Want personalised advice about hay fever treatment options? Speak with an allergy specialist who can assess your symptoms and history.