Allergy injections can offer real relief for some people, though results vary from person to person. They typically require a sustained course over several years rather than a one-off fix, but they can meaningfully reduce symptoms through a process called desensitisation.
How Do Allergy Injections Work?
Allergy injections, also known as immunotherapy, are given over a period of time – usually three to five years – and can significantly reduce symptoms, with some people experiencing near-complete relief. That relief isn't always permanent, though in some cases symptoms can improve substantially and remain that way long-term, though this is comparatively less common.
Once the specific allergen has been identified, a doctor will begin a course of immunotherapy, typically starting with around two injections per week. Each injection contains a small, carefully controlled amount of the allergen causing the reaction, gradually increased over time to build tolerance – this build-up period is known as desensitisation. Dosage and injection frequency are adjusted by your doctor as treatment progresses, usually with longer gaps between injections later in the course. The three-to-five-year timeframe reflects what's needed to build immunity to a level that meaningfully reduces symptoms.
Are There Any Side Effects?
Most side effects are minor and not life-threatening. Doctors typically ask patients to remain in the waiting room for a set period after each injection, purely as a precaution in case of a rare, more serious reaction.
Common, localised reactions during the waiting period or a few hours afterwards include:
- Redness or inflammation
- Slight swelling
- Itchiness or irritation at the injection site
These are common and usually resolve quickly. Contact your doctor if you're ever in doubt.
Rarer reactions that do need attention include:
- Persistent sneezing or nasal congestion
- Throat swelling
- Chest tightness or difficulty breathing
In very rare cases, anaphylaxis can occur, causing dangerously low blood pressure and breathing difficulty – this requires immediate emergency treatment, which is exactly why the post-injection waiting period matters, since anaphylaxis develops rapidly. This is genuinely rare, but it's important to complete the full course of injections as prescribed once started – missing doses and then restarting can itself increase the risk of a serious reaction.
I'm Scared of Injections – Is There an Alternative?
A controlled course of injections offers the strongest effect, and this varies depending on what you're allergic to. Since injections are typically needed two to three times a week in the early stages, many people find the initial weeks are the hardest, with it becoming more routine afterwards. Oral medications can help reduce allergic reactions, but generally aren't as effective as a full injection course. Your doctor may already have tried oral treatment before recommending immunotherapy.
Can Any Allergy Be Treated With Injections?
Not every allergy is suitable for this treatment. Immunotherapy injections can help with:
- Seasonal allergies such as hay fever, triggered by pollen from trees, grasses and other plants
- Insect sting allergies (wasp stings being a common example)
- Year-round allergens such as dust mites, mould and pet hair
Injections aren't currently available for food allergies, as this hasn't been approved by the relevant regulatory bodies for drug therapy. If a food allergy is what you're dealing with, testing and careful avoidance remain the primary approach – our allergy test guide covers how that process works.
How Do I Find Out If I'm Allergic to Something?
The most reliable first step is seeing a GP as soon as you notice unusual irritation, rashes or other symptoms. They'll typically ask about recent changes – new pets, different washing powder, dietary changes – before carrying out a skin prick test. This involves gently introducing a small amount of the suspected allergen just under the skin; a reaction within about 15 minutes, shown as swelling or redness, indicates a likely allergy to that substance.
Some doctors also use blood tests to help identify allergies, though these are often used alongside a skin prick test rather than as a standalone diagnostic.
